bug#12309: 24.2.50; Option `(bookmark-)version-control': Use :tag so doc string matches menu

[Drew Adams]

The doc strings of these variables speak of values t, nil, `never', and
(for `bookmark-version-control) `nospecial'.
 
The Value Menu for `version-control' shows "Never", "If existing",
"Always".  At least you can see the correspondence, because the same
words are used - you can tell that "Always" corresponds to "always" in
the doc string, which corresponds to value `t'.
 
The Value Menu for `bookmark-version-control' shows "nil", "never",
"nospecial", and "Other".  It is "Other" that is problematic for a user
- it doesn't correspond to anything in the doc string (except by process
of elimination).
 
Please use :tag to make things clearer.  In particular, use something
besides "Other" (the default name) for `t' (i.e., for any other non-nil value
than `never' and `nospecial').
 

In GNU Emacs 24.2.50.1 (i386-mingw-nt5.1.2600)
 of 2012-08-26 on MARVIN
Bzr revision: 109788 dmantipov@yandex.ru-20120827041533-3cy7pdjdqz14o90c
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'