pgsql: Allow binary-coercible cases in ri_HashCompareOp; there are some

Log Message:
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Allow binary-coercible cases in ri_HashCompareOp; there are some such cases
that are not handled by find_coercion_pathway, notably composite->RECORD.
Now that 8.4 supports composites as primary keys, it's worth dealing with
this case.

Modified Files:
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pgsql/src/backend/utils/adt:
ri_triggers.c (r1.114 -> r1.115)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/ri_triggers.c?r1=1.114&r2=1.115)