[1.2.X] Fixed #13723 -- Improved the legibility of hyperlinks included in...

[1.2.X] Fixed #13723 -- Improved the legibility of hyperlinks included in admin validation error messages. Thanks to Sebastian Noack for the suggestion and patch.

Backport of r13659 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@13662 bcc190cf-cafb-0310-a4f2-bffc1f526a37