[1.6.x] Tweaked proj string regex in gis tests

Backport of 4367c637d6 from master
[1.6.x] Fixed #20838 -- Fixed Geodjango spatialrefsys test failure with postgis-2.0.3

Backport of fd0d486467 from master
[1.6.x] Fixed #18681 -- GenericInlineModelAdmin.get_formset() no longer bypasses get_fieldsets().

Refs 23e1b59 which already fixed this issue for ModelAdmin and InlineModelAdmin.

Backport of a0ed2f9260 from master