Long overdue merge.

Long overdue merge.
Don't require `compile' since it seems unnecessary.
For all internal variables and functions the docstring comments have
been converted into proper docstrings
(bibtex-maintainer-address, bibtex-maintainer-salutation)
(bibtex-version): Remove support for bug reporting.
(bibtex-field-delimiters, bibtex-entry-delimiters)
(bibtex-sort-ignore-string-entries, bibtex-maintain-sorted-entries)
Replace make-variable-buffer-local by make-local-variable for
(bibtex-entry-format): New tag `required-fields'.
(bibtex-maintain-sorted-entries): New var.
(bibtex-sort-entry-class, bibtex-sort-entry-class-alist): New vars.
(bibtex-predefined-month-strings, bibtex-predefined-strings):
Make into alists with pairs (abbreviation expansion).
(bibtex-autokey-titleword-change-strings)
(bibtex-autokey-transcriptions): Make into alists.
Add new replacement pairs.
(bibtex-autokey-use-crossref): New var.
Replace bibtex-autokey-year-use-crossref-entry because updated code
for autokey generation handles crossrefs independently of
particular fields.
(bibtex-reference-key, bibtex-mode-syntax-table):
Remove = because it can't be part of a string's key.
(bibtex-complete-key-cleanup): New var.
(bibtex-complete): Merge bibtex-complete-string and bibtex-complete-key
into it (and bind to M-tab).
(bibtex-valid-entry-re, bibtex-any-valid-entry-re)
(bibtex-valid-entry-whitespace-re, bibtex-empty-field-re)
(bibtex-quoted-string-re): New vars.
(bibtex-field-name-for-parsing): Don't make-variable-buffer-local.
(zmacs-regions): Declare to quieten the byte-compiler.
(bibtex-comment-start): Don't include the space.
(bibtex-font-lock-syntactic-keywords): New var.
(bibtex-font-lock-keywords): Remove the entry for @Comment.
(bibtex-parse-field-string): Merge the functionality of
bibtex-parse-field-string-braced, bibtex-parse-quoted-string and
bibtex-parse-field-string-quoted.
(bibtex-search-forward-field-string): Remove.
(bibtex-parse-association): Use when.
(bibtex-parse-field-name): Use when.
(bibtex-parse-field-text): Use when and cond.
(bibtex-parse-field): Use let.
(bibtex-search-forward-field, bibtex-search-backward-field):
Make bound optional, use let, setq, and cddr.
(bibtex-start-of-field, bibtex-start-of-name-in-field)
(bibtex-end-of-name-in-field): Use nth.
(bibtex-name-in-field, bibtex-text-in-field-bounds)
(bibtex-text-in-field, bibtex-type-in-head, bibtex-key-in-head)
(bibtex-text-in-string): New functions.
(bibtex-reference-key-in-string): New fun.  Merge of
bibtex-start-of-reference-key-in-string and
bibtex-end-of-reference-key-in-string.
(bibtex-parse-string-prefix): Use let and when.
(bibtex-parse-string-postfix): Use when.
(bibtex-search-forward-string, bibtex-search-backward-string):
Use save-excursion and setq.
(bibtex-member-of-regexp): Use let.
(bibtex-assoc-of-regexp): Use caar und let.
(bibtex-skip-to-valid-entry): Return buffer position.
(bibtex-map-entries): Use save-excursion.
(bibtex-progress-message): Simplify.
(bibtex-search-entry): Use skip-chars-forward, when, save-match-data.
(bibtex-move-outside-of-entry): Handle the case that point is before
first entry.
(bibtex-enclosing-field): Use save-excursion, when.
(bibtex-format-field-delimiters): Merge into bibtex-format-entry.
(bibtex-enclosing-entry-maybe-empty-head): Simplify.
(bibtex-format-entry): Simplify.  Handle new tag required-fields of
bibtex-entry-format.
(bibtex-autokey-abbrev): Accept negative values of len.
(bibtex-autokey-get-field, bibtex-autokey-demangle-title): New funs.
(bibtex-autokey-get-namefield, bibtex-autokey-get-namelist)
(bibtex-autokey-get-yearfield-digits, bibtex-autokey-get-yearfield)
(bibtex-autokey-get-titlestring): Remove.
(bibtex-autokey-get-names): Simplify.
(bibtex-autokey-get-titles): Rename to bibtex-autokey-get-title.
(bibtex-autokey-demangle-name): Simplify, avoid error messages.
(bibtex-generate-autokey): Simplify.
(bibtex-parse-keys): Simplify, use push.
(bibtex-parse-strings): New fun similar to bibtex-parse-keys.
(bibtex-string-files-init): New fun.
(bibtex-parse-buffers-stealthily): Use bibtex-parse-keys,
bibtex-string-files-init and bibtex-parse-strings.
(bibtex-complete): Rename to bibtex-complete-internal, use push,
bibtex-reference-key-in-string, no sorting.
(bibtex-complete-string-cleanup): New fun, displays expansion of
completed strings.
(bibtex-choose-completion-string): New fun.  Required for
choose-completion-string-functions.
(bibtex-do-auto-fill): Remove.  Set fill-prefix in bibtex-mode.
(bibtex-pop): Simplify.
(bibtex-mode): Move setting of bibtex-string to bibtex-parse-strings.
Set choose-completion-string-functions.
(bibtex-print-help-message,bibtex-make-field, bibtex-end-of-entry)
(bibtex-count-entries): Simplify.
(bibtex-entry-index, bibtex-lessp): New funs for generalized sorting
scheme of indices, see bibtex-maintain-sorted-entries.
(bibtex-sort-buffer): Use bibtex-lessp for sorting.
(bibtex-find-crossref, bibtex-find-entry): New funs.
(bibtex-find-entry-location): Rename to bibtex-prepare-new-entry, use
bibtex-lessp, Simplify.
(bibtex-validate): Simplify.  Fixe bug of internal variable
questionable-month.
(bibtex-remove-OPT-or-ALT): Use when.
(bibtex-remove-delimiters, bibtex-kill-field, bibtex-kill-entry)
(bibtex-clean-entry, bibtex-fill-entry, bibtex-reformat): Simplify.
(bibtex-convert-alien): Use deactivate-mark rather than the
non-existent bibtex-mark-active variable.
(bibtex-complete-string, bibtex-complete-key): Merge into new
`smart' defun bibtex-complete.
(bibtex-String): Update for new sorting scheme, distinguish empty and
non-empty key strings.