[1.0.X] Fixed #10406 -- Fixed some problems with model inheritance and pk fields.

Manually specifying both a OneToOneField(parent_link=True) and separate a
primary key field was causing invalid SQL to be generated. Thanks to Ramiro
Morales for some analysis on this one.

Backport of r9971 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.0.X@9973 bcc190cf-cafb-0310-a4f2-bffc1f526a37