Fixe #6131 -- Fixed a problem with expired keys in the locmem cache. Based on...

Fixe #6131 -- Fixed a problem with expired keys in the locmem cache. Based on a patch from sherbang.

In passing, changed the get() method to use a similar style to has_key() and made add() fractionally faster with the same sort of change (only compute time.time() when we really need it).


git-svn-id: http://code.djangoproject.com/svn/django/trunk@6904 bcc190cf-cafb-0310-a4f2-bffc1f526a37