Fixed #10237 -- Corrected the handling of self-referential m2m fields when...

Fixed #10237 -- Corrected the handling of self-referential m2m fields when using multi-table inheritance. Thanks to Justin Lilly for the report and patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@10550 bcc190cf-cafb-0310-a4f2-bffc1f526a37