[1.1.X] Fixed #12399 -- Added handling for memcache timeouts longer than 30...

[1.1.X] Fixed #12399 -- Added handling for memcache timeouts longer than 30 days. Thanks to houdinihound for the report, and gciotta for the patch.

Backport of r12408 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.1.X@12412 bcc190cf-cafb-0310-a4f2-bffc1f526a37