[1.1.X] Fixed #12438 -- now use `GEOSFree` to free string pointers allocated...

[1.1.X] Fixed #12438 -- now use `GEOSFree` to free string pointers allocated within GEOS when available; now parse out subminor version, and added a `GEOS_VERSION` tuple.

Backport of r11979 from trunk.


git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.1.X@11980 bcc190cf-cafb-0310-a4f2-bffc1f526a37