Fixed #23043: alter_field drops defaults too
Fixed #23039: Don't try to serialize unmanaged models in tests
Fixed #22975: Don't call rename SQL if not needed
Fixed #23009: Shorten FK identifiers in add_field and make consistent
Fixed #23014: Renaming not atomic with unique together
Fixed #23064 -- Added lib detection support for GDAL 1.10/1.11

Note that GDAL 1.11 is not yet officially supported, until someone
has tested it and can confirm it has no issues with Django.
Replaced instances of 'his/her' with 'their'.
Fixed typo in PermissionsMixin.groups.help_text.