bug#14398: 24.3.50; Customize: `Revert...' and `Apply'

[Drew Adams]

1. The `Revert...' menu items should be controled by either :enable or
:visible.  It makes no sense to show a user an active menu item `Undo
Edits in Customization Buffer' if there have been no edits.  After a
user clicks this, undoing any edits, this menu item should disappear or
be dimmed.  Similarly for other menu items.
 
2. `Apply' is not helpful as is.  The name does not sufficiently
indicate what it does (apply what? to what?).  The help echo is also not
helpful enough: `Apply settings (for current session only)'.  What
settings?  And again, if no settings have been changed (edited) then
this button should not even be available.  Its presence when it is a
no-op just confuses.
 
In GNU Emacs 24.3.50.1 (i386-mingw-nt5.1.2600)
 of 2013-05-10 on ODIEONE
Bzr revision: 112542 rgm@gnu.org-20130510102119-fklj7xlajezey0tr
Windowing system distributor `Microsoft Corp.', version 5.1.2600
Configured using:
 `configure --with-gcc (4.7) --no-opt --enable-checking --cflags
 -IC:/Devel/emacs/build/include --ldflags -LC:/Devel/emacs/build/lib'