pgsql: Fix incorrect patch that removed permission checks on inheritance

Log Message:
-----------
Fix incorrect patch that removed permission checks on inheritance child
tables --- the parent table no longer got checked, either. Per bug #5458
from Takahiro Itagaki.

Modified Files:
--------------
pgsql/src/backend/optimizer/prep:
prepunion.c (r1.181 -> r1.182)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/optimizer/prep/prepunion.c?r1=1.181&r2=1.182)