* lisp/wdired.el: Apply text properties lazily

* lisp/wdired.el: Apply text properties lazily

Entering wdired was taking time proportional to the size of the directory,
making it inconvenient to quickly enter wdired just to rename one or two
files in a large directory.

(wdired-mode-map): Rebind `self-insert-command`.
(wdired--perm-beg, wdired--perm-end): New vars.
(wdired--col-perm, wdired--old-content, wdired--old-point)
(wdired--old-marks): Rename vars, using "--" rather than "-".
All users updated.
(wdired--before-change-fn): New function.
(wdired-change-to-wdired-mode): Use it `before-change-functions`
instead of eagerly putting the various text properties here.
(wdired--set-permission-bounds, wdired--current-column)
(wdired--point-at-perms-p, wdired--line-preprocessed-p):
New auxiliary functions.
(wdired--self-insert): New command.
(wdired--preprocess-files, wdired--preprocess-symlinks)
(wdired--preprocess-perms): Add "--" to the name.  Make it operate only
on the current line.  Use `with-silent-modifications`.
(wdired-abort-changes): Use `with-silent-modifications`.