bug#14942: 24.3.50; Improve key descriptions for facemenu menu items

[Drew Adams <drew.adams@oracle.com>]

`C-h f facemenu-set-invisible' says that the command is bound to
<C-down-mouse-2> <sp> v, <menu-bar> <edit> <props> <sp> v.

Good luck trying to understand that, Ms User.  And yet it is so close.

This would be a lot more helpful for users if we simply used reasonable
names for the menu-item pseudo-function keys.  Instead of <sp> use
<special-properties> and things suddenly become much clearer.  Likewise,
use <text-properties> instead of <props>.  Likewise, use <invisible>
instead of just [?v].

There is no reason to take shortcuts coding this kind of thing.  Keep
in mind that the names used for menu-item keys are part of the user
interface.  Please make an effort to provide names that help users
instead of just looking for a quick abbreviation.

In GNU Emacs 24.3.50.1 (i686-pc-mingw32)
 of 2013-07-14 on ODIEONE
Bzr revision: 113423 lekktu@gmail.com-20130715004922-i67tg2ois14h3fpm
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --prefix=/c/Devel/emacs/binary --enable-checking=yes,glyphs
 CFLAGS='-O0 -g3' CPPFLAGS='-Ic:/Devel/emacs/include'
 LDFLAGS='-Lc:/Devel/emacs/lib''