pgsql: Fix oversight in the previous patch that made LIKE throw error

Log Message:
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Fix oversight in the previous patch that made LIKE throw error for \ at the
end of the pattern: the code path that handles \ just after % should throw
error too.  As in the previous patch, not back-patching for fear of breaking
apps that worked before.

Modified Files:
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    pgsql/src/backend/utils/adt:
        like_match.c (r1.28 -> r1.29)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/like_match.c?r1=1.28&r2=1.29)