bug#11299: 24.1.50; Make `customize-mode' work for minor modes too, or define `customize-minor-mode'

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

1. First, a doc quibble and a question about the status of this command.
`(elisp) Derived Modes' says, "Only the (still experimental and
unadvertised) command `customize-mode' currently uses this."
 
It has said this since at least Emacs 22.  If it was an experiment (how
so? no explanation anywhere, AFAICT), presumably it is over now?  Or at
least explain in what way it is experimental.  Does it have problems?
If so what?  It does not help users to characterize something as
"experimental" if you do not describe the experiment or the associated
questions/problems.
 
And `customize-mode' is of course not at all "unadvertised", since it is
documented, including here, in this part of the manual.  This kind of
writing, characterizing something as experimental or unadvertised does
not belong in the manual.  And it only becomes more inappropriate with
time and neglect.
 

2. AFAICT, there is nothing in the definition or use of `customize-mode'
that necessarily limits it to major modes.  The only thing that limits
it this way is that `major-mode' is hard-coded in its definition.
 
Even the use of `custom-group-of-mode' in the definition applies equally
to minor modes, IIUC.  Likewise, the use of `completion-regexp-list'
with "-mode\\'" applies to minor modes as well.
 
So please release it from its limitation to major modes.  Minor modes
can have defcustoms and deffaces and defgroups too.
 
It is OK for the default to be the current major mode, but the use of a
prefix arg (completion for a mode name) should at least allow for minor
modes as well as major modes.
 

In GNU Emacs 24.1.50.1 (i386-mingw-nt5.1.2600)
 of 2012-04-19 on MARVIN
Bzr revision: 107968 monnier@iro.umontreal.ca-20120419220225-gijdcbfxuiqy5dhb
Windowing system distributor `Microsoft Corp.', version 5.1.2600
Configured using:
 `configure --with-gcc (4.6) --no-opt --enable-checking --cflags
 -ID:/devel/emacs/libs/libXpm-3.5.8/include
 -ID:/devel/emacs/libs/libXpm-3.5.8/src
 -ID:/devel/emacs/libs/libpng-dev_1.4.3-1/include
 -ID:/devel/emacs/libs/zlib-dev_1.2.5-2/include
 -ID:/devel/emacs/libs/giflib-4.1.4-1/include
 -ID:/devel/emacs/libs/jpeg-6b-4/include
 -ID:/devel/emacs/libs/tiff-3.8.2-1/include
 -ID:/devel/emacs/libs/gnutls-3.0.9/include
 -ID:/devel/emacs/libs/libiconv-1.13.1-1-dev/include
 -ID:/devel/emacs/libs/libxml2-2.7.8/include/libxml2'