Fixed situation when parent abstract model declares related_name='+'
and child models had an invalid queryset.
Backport of f7b297815819153b53dc1125d3f42869fb1b7ebc from master
Added support for multiple m2m fields with the same 'to' model
and with related_name set to '+'.
Backport of 4ee08958f154594b538207a53c1d457687b3f7ae from master
This reverts commit e8171daf0cd7f0e070395cb4c850c17fea32f11d.
A new solution is forthcoming.
Backport of 0e489c19f1554ecfd9825daacfbac73be8ce723e from master
The reason for the regression was that the GenericForeignKey field isn't
something meta.get_field_by_name() should return. The reason is that a
couple of places in Django expects get_field_by_name() to work this way.
It could make sense to return GFKs from get_field_by_name(), but that
should likely be done as part of meta refactoring or virtual fields
refactoring patches.
Thanks to glicerinu@gmail.com for the report and to Tim for working on
the issue.
