[1.0.X] Fixed #11245, #11246 -- Fixed validity check of `GeoIP` pointers and...

[1.0.X] Fixed #11245, #11246 -- Fixed validity check of `GeoIP` pointers and leaking of their references; also clarified initialization, fixed a stale test, added comments about version compatibility, and did some whitespace cleanup.

Backport of r10979 from trunk.


git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.0.X@10980 bcc190cf-cafb-0310-a4f2-bffc1f526a37