* calendar/todos.el: Remove old commentary from todo-mode.el; add

* calendar/todos.el: Remove old commentary from todo-mode.el; add
and revise further doc strings and comments; require cl.el at
compile time for remove-duplicates; use function powerset from
http://rosettacode.org/wiki/Power_set#Common_Lisp (GFDL); further
code rearrangement.  Add adapted version of diary-goto-entry as comment.
(todos-file-top, todos-archived-categories-buffer)
(todos-save-top-priorities-too, todos-toggle-item-diary-inclusion)
(todos-save-top-priorities, todos-reset-separator)
(todos-switch-todos-file, todos-item-string-start, todos-counts)
(todos-string-count-lines, todos-string-multiline-p)
(todos-display-categories-alphabetically): Remove.
(todos-insert-item-ask-date, todos-insert-item-ask-date-time)
(todos-insert-item-ask-date-time-for-diary)
(todos-insert-item-ask-date-time-for-diary-here)
(todos-insert-item-ask-date-time-here)
(todos-insert-item-ask-date-maybe-notime)
(todos-insert-item-ask-date-maybe-notime-for-diary)
(todos-insert-item-ask-date-maybe-notime-for-diary-here)
(todos-insert-item-ask-date-maybe-notime-here)
(todos-insert-item-ask-date-for-diary)
(todos-insert-item-ask-date-for-diary-here)
(todos-insert-item-ask-date-here, todos-insert-item-ask-dayname)
(todos-insert-item-ask-dayname-time)
(todos-insert-item-ask-dayname-time-for-diary)
(todos-insert-item-ask-dayname-time-for-diary-here)
(todos-insert-item-ask-dayname-time-here)
(todos-insert-item-ask-dayname-maybe-notime)
(todos-insert-item-ask-dayname-maybe-notime-for-diary)
(todos-insert-item-ask-dayname-maybe-notime-for-diary-here)
(todos-insert-item-ask-dayname-maybe-notime-here)
(todos-insert-item-ask-dayname-for-diary)
(todos-insert-item-ask-dayname-for-diary-here)
(todos-insert-item-ask-dayname-here, todos-insert-item-ask-time)
(todos-insert-item-ask-time-for-diary)
(todos-insert-item-ask-time-for-diary-here)
(todos-insert-item-ask-time-here)
(todos-insert-item-maybe-notime)
(todos-insert-item-maybe-notime-for-diary)
(todos-insert-item-maybe-notime-for-diary-here)
(todos-insert-item-maybe-notime-here)
(todos-insert-item-for-diary, todos-insert-item-for-diary-here)
(todos-insert-item-here): Remove; all of these are now generated
on loading (some with the same name, most with other names.)
(todos-item-counts, todos-display-categories-alphabetically)
(todos-display-categories-sorted-by-todo)
(todos-display-categories-sorted-by-diary)
(todos-display-categories-sorted-by-done)
(todos-display-categories-sorted-by-archived): Comment out.
(todos-comment-string, todos-mode-line-function)
(todos-filter-function, todos-priorities-rules)
(todos-visit-files-commands, todos-categories-totals-label)
(todos-use-only-highlighted-region, todos-diary-nonmarking):
New defcustoms.
(todos-mark, todos-comment): New faces.
(todos-comment-face): Corresponding new variable.
(todos-categories-full, todos-global-current-todos-file)
(todos-first-visit, todos-insertion-commands-args-genlist)
(todos-insertion-commands-args, todos-insertion-commands-names)
(todos-insertion-commands, todos-insertion-commands-arg-key-list)
(todos-top-priorities-widgets, todos-date-from-calendar)
(todos-item-mark, todos-categories-with-marks): New variables.
(todos-mode-line-control, todos-reset-global-current-todos-file)
(todos-gen-arglists, todos-insertion-command-name)
(todos-insertion-key-bindings, todos-unload-hook)
(todos-filter-items, todos-set-date-from-calendar)
(todos-comment-string-matcher, todos-after-find-file)
(todos-reset-nondiary-marker, todos-reset-done-string)
(todos-reset-comment-string, todos-show-current-file)
(todos-item-marked-p, todos-total-item-counts): New functions.
(todos-define-insertion-command): New macro.
(todos-toggle-mark-item, todos-mark-category)
(todos-unmark-category, todos-set-top-priorities)
(todos-merged-diary-items, todos-regexp-items)
(todos-merged-regexp-items, todos-custom-items)
(todos-merged-custom-items, todos-comment-done-item)
(todos-archive-category-done-items, todos-unarchive-items)
(todos-print-to-file): New commands.
(todos-done-separator): Change :set function.
(todos-done-string): Uncomment :initialize and :set functions.
(todos-files): Use file-truename.
(todos-show-current-file): Rename from
todos-auto-switch-todos-file and change :set function accordingly.
(todos-font-lock-keywords): Use todos-comment-string-matcher;
change names of other matcher functions to new *-matcher.
(todos-category-number): Change initial value.
(todos-insertion-map): Use todos-insertion-key-bindings to
generate key definitions.
(todos-mode-map): Don't suppress digit keys, so they can supply
prefix arguments; add new and change some existing bindings.
(todos-archive-mode-map): Change a key binding.
(todos-categories-mode-map): Comment out a key binding.
(todos-filter-items-mode-map): Rename from
todos-top-priorities-mode-map.
(todos-mode): Make todos-current-todos-file,
todos-categories-full, todos-categories, todos-first-visit,
todos-category-number, todos-show-done-only,
todos-categories-with-marks local variables and set them; add
todos-show-current-file to pre-command-hook, todos-after-find-file
to post-command-hook and todos-reset-global-current-todos-file to
kill-buffer-hook.
(todos-archive-mode): Make todos-current-todos-file,
todos-categories and todos-category-number local variables and set
them; add todos-after-find-file to post-command-hook.
(todos-raw-mode): New derived major mode.
(todos-categories-mode): Don't set font-lock-defaults and
buffer-read-only; make todos-current-todos-file and
todos-categories local variables and set them.
(todos-filter-items-mode): Rename from todos-top-priorities-mode-map.
(todos-quit): Don't reset todos-categories on quitting
todos-categories-mode; handle quitting todos-filter-items-mode.
(todos-show): Simplify; when visiting an archive file switch to
corresponding Todos file; use todos-first-visit.
(todos-view-archived-items): Simplify; call todos-category-number.
(todos-show-archive): Rename from todos-switch-to-archive and
adjust callers; simplify.
(todos-toggle-display-date-time): Add optional argument to toggle
display in entire file.
(todos-top-priorities): Use todos-filter-items, which now contains
the previous core of this command.
(todos-merged-top-priorities, todos-diary-items):
Use todos-filter-items.
(todos-forward-category): Add optional argument to go to the
previous category.
(todos-backward-category): Use todos-forward-category.
(todos-jump-to-category): Refine implementation.
(todos-forward-item, todos-backward-item): Fix movement from todo
to done item and vice versa.
(todos-add-file): Remove argument and simplify.
(todos-rename-category): Use todos-current-todos-file and
todos-mode-line-function; set todos-categories with
todos-set-categories.
(todos-delete-category): Ask what to do if category has archived items.
(todos-raise-category): Ensure modified todos-categories is added
to file's categories sexp.
(todos-move-category): Improve implementation, especially handling
of archived categories.
(todos-merge-category): Tweak; set item counts.
(todos-insert-item): Improve handling of various argument values;
add new argument values to control marking of diary items and to
use region for item body.
(todos-insert-item-from-calendar): Use todos-global-current-todos-file.
(todos-delete-item, todos-edit-item-header): Handle marked items.
(todos-edit-item): Incorporate functionality of removed
todos-string-multiline-p.
(todos-edit-multiline): Use set-window-buffer instead of
switch-to-buffer.
(todos-edit-quit): Don't save on quitting; use todos-show instead
of todos-category-select.
(todos-raise-item-priority): Add argument to lower priority;
improve handling of top priority items in todos-filter-items-mode;
restore marks.
(todos-lower-item-priority): Use todos-raise-item-priority.
(todos-set-item-priority): Increment maximum number if item is new.
(todos-move-item): Handle marked items; delay changing category
moved from till after movement to avoid restoring if user cancels
before insertion.
(todos-item-done): Add optional argument to insert comment; fix
item counts and update sexp.
(todos-item-undo): Fix item counts and update.
(todos-archive-done-item-or-items): Rename from
todos-archive-done-items; add optional argument to archive all
items in category; handle marked items.
(todos-unarchive-category): Use todos-unarchive-items.
(todos-toggle-diary-inclusion): Incorporate functionality of
removed todos-toggle-item-diary-inclusion; handle marked items.
(todos-print): Add optional argument to print to file.
(todos-done-string-start): Don't use todos-nondiary-start.
(todos-date-string-matcher, todos-time-string-matcher)
(todos-done-string-matcher, todos-category-string-matcher): Rename
from *-match and adjust callers.
(todos-wrap-and-indent): Use set instead of setq for local variables.
(todos-prefix-overlays): Improve overlay handling.
(todos-reset-categories): Fix and complete implementation.
(todos-toggle-show-current-file): Rename from
todos-toggle-switch-todos-file-noninteractively.
(todos-category-select): Use todos-mode-line-function.
(todos-item-start): Comment out code used by removed function.
(todos-remove-item): Handle presence of both prefix/number and
mark overlays.
(todos-get-count): Simplify.
(todos-set-count): Change argument list and adjust callers; simplify.
(todos-set-categories): Handle new archive files; use
todos-categories-full and todos-ignore-archived-categories.
(todos-truncate-categories-list): Use todos-categories-full.
(todos-update-categories-sexp): Use kill-region instead of
kill-line; use todos-categories-full.
(todos-read-file-name): Add argument to require existing file and
adjust callers; use file-truename.
(todos-read-category): Remove argument to require existing
category and delegate it to completing-read in function body.
(todos-validate-category-name): Make empty string prompt only for
initial category name.
(todos-read-date): Use = instead of eq for testing if month = 13,
and if it is, set monthname to *.
(todos-display-categories): Use todos-global-current-todos-file;
use set-window-buffer instead of switch-to-buffer; add a line
showing item count totals.
(todos-padded-string): Use the longest of category name or label.
(todos-descending-counts): Rename from
todos-descending-counts-store and adjust users.
(todos-insert-category-line): Adjust format; use mapconcat; kill
buffer after jumping to category.