Customize doc strings do not respect \\<...> and \\[...]

[Drew Adams]

emacs -q

(defcustom foo nil
  "*Behavior of `\\<my-map>\\[my-cmd]' when foobaz is in the wind."
  :type 'boolean)

Then, `C-h v foo' shows the doc string correctly as, say, "Behavior of
`M-a' when foobaz is in the wind."  However, when you click the
Customize link and get to the Customize buffer, the key bindings are
not substituted in the doc string. You see this:

Behavior of `\<my-map>\[my-cmd]' when foobaz is in the wind.

Note that one level of backslash is removed.

In GNU Emacs 22.0.50.1 (i386-mingw-nt5.1.2600)
 of 2005-06-26 on NONIQPC
X server distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc
(3.3) --cflags -I../../jpeg-6b-3/include -I../../libpng-1.2.8/include -I../.
./tiff-3.6.1-2/include -I../../xpm-nox-4.2.0/include -I../../zlib-1.2.2/incl
ude'