Fixed #14290 -- Made format localization faster by caching the format modules....

Fixed #14290 -- Made format localization faster by caching the format modules. Thanks, Teemu Kurppa and Anssi Kääriäinen for the report and initial patches.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@13898 bcc190cf-cafb-0310-a4f2-bffc1f526a37