pgsql: Restore enforce_generic_type_consistency's pre-8.3 behavior of

Log Message:
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Restore enforce_generic_type_consistency's pre-8.3 behavior of allowing an
actual argument type of ANYARRAY to match an argument declared ANYARRAY,
so long as ANYELEMENT etc aren't used. I had overlooked the fact that this
is a possible case while fixing bug #3852; but it is possible because
pg_statistic contains columns declared ANYARRAY. Per gripe from Corey Horton.

Modified Files:
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pgsql/src/backend/parser:
parse_coerce.c (r2.171 -> r2.172)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/parse_coerce.c?r1=2.171&r2=2.172)
pgsql/src/test/regress/expected:
polymorphism.out (r1.15 -> r1.16)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/polymorphism.out?r1=1.15&r2=1.16)
pgsql/src/test/regress/sql:
polymorphism.sql (r1.8 -> r1.9)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/polymorphism.sql?r1=1.8&r2=1.9)