bug#12067: 24.1; improper menu formatting with multiple \t chars

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

emacs -Q

(defcustom foo [:ascii:]
  "..."
  :type
  '(choice :tag "Foobar"
    (const :tag "A\t\t- [:ascii:]"                                [:ascii:])
    (const :tag "Bbbbbb\t\t- [:nonascii:]"                        [:nonascii:])
    (const :tag "Cccccccccccc\t\t- [:word:]"                      [:word:])
    (const :tag "Dddddddddddddddddddddddddd\t\t- [:alnum:]"       [:alnum:])
    (const :tag "Eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee\t- [:alpha:]" [:alpha:]))
  :group 'convenience)

M-x customize-option foo
 
Click button Value Menu to see the menu.  Each time \t\t is used, there
is a rectangular artifact added also.
 
It turns out that using only a single \t does the right thing in terms
of alignment in this case.  But shouldn't multiple \t's let you tab
(indent) further, as they do in text buffers, doc strings, etc.?  And
presumably \t\t should not draw a rectangle, in any case.
 

In GNU Emacs 24.1.1 (i386-mingw-nt5.1.2600)
 of 2012-06-10 on MARVIN
Windowing system distributor `Microsoft Corp.', version 5.1.2600
Configured using:
 `configure --with-gcc (4.6) --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'