pgsql: Change ILIKE to invoke lower() and then do plain LIKE comparison

Log Message:
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Change ILIKE to invoke lower() and then do plain LIKE comparison when
working in a multibyte encoding. This fixes the problems exhibited in
bug #1931 and other reports of ILIKE misbehavior in UTF8 encoding.
It's a pretty grotty solution though --- should rethink how to do it
after we install better locale support, someday.

Modified Files:
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pgsql/src/backend/utils/adt:
like.c (r1.64 -> r1.65)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/like.c.diff?r1=1.64&r2=1.65)