bug#15682: 24.3.50; `:link' in `defgroup' does not respect `mouse-1-click-follows-link'

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

emacs -Q

In *scratch*, evaluate this:

(defgroup foo nil
  "..." :prefix "foo-" :group 'editing
  :link '(url-link "http://www.emacswiki.org/"))

(defcustom foobar t "..." :type 'boolean :group 'foo)

M-x set-variable mouse-1-click-follows-link nil
M-x customize-option foobar

Click the link `http://www.emacswiki.org/' using `mouse-1'.  The link is
followed - it should not be followed.

Note that `mouse-on-link-p' returns `t' for positions on this link, and
such positions have face `custom-link', property `follow-link' with
value `mouse-face', and property `mouse-face' with a face value, all of
which show further that the behavior violates the mandate of
`mouse-1-click-follows-link'.

Quite annoying.  Emacs should not overrule user settings like this.
This is not a regression: it has been broken from the outset (broken in
all Emacs versions that support `:link').

In GNU Emacs 24.3.50.1 (i686-pc-mingw32)
 of 2013-10-19 on LEG570
Bzr revision: 114715 rgm@gnu.org-20131019023520-s8mwtib7xcx9e05w
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --enable-checking 'CFLAGS=-O0 -g3' CPPFLAGS=-DGLYPH_DEBUG=1'