Fixed #11966 -- Made it possible to use a percent sign in a translation...

Fixed #11966 -- Made it possible to use a percent sign in a translation message id. Thanks for the patch, Claude Paroz.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14459 bcc190cf-cafb-0310-a4f2-bffc1f526a37