Fixes for checking unique constraints on RI creation

Stephan Szabo <sszabo@megazone23.bigpanda.com> writes:

I believe this should fix the issue that Philip Warner
noticed about the check for unique constraints meeting the
referenced keys of a foreign key constraint allowing the
specification of a subset of a foreign key instead of
rejecting it. I also added tests for a base case of
this to the foreign key and alter table tests and patches
for expected output.

Applied.

regards, tom lane