[1.2.X] Fixed a case-sensitivity bug in Oracle introspection that was...

[1.2.X] Fixed a case-sensitivity bug in Oracle introspection that was preventing inspectdb from identifying foreign keys.
Backport of r15785 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@15786 bcc190cf-cafb-0310-a4f2-bffc1f526a37