pgsql: Restore enforce_generic_type_consistency's pre-8.3 behavior of

Log Message:
-----------
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.

Tags:
----
REL8_3_STABLE

Modified Files:
--------------
    pgsql/src/backend/parser:
        parse_coerce.c (r2.161.2.1 -> r2.161.2.2)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/parse_coerce.c?r1=2.161.2.1&r2=2.161.2.2)
    pgsql/src/test/regress/expected:
        polymorphism.out (r1.12 -> r1.12.2.1)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/polymorphism.out?r1=1.12&r2=1.12.2.1)
    pgsql/src/test/regress/sql:
        polymorphism.sql (r1.5 -> r1.5.2.1)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/polymorphism.sql?r1=1.5&r2=1.5.2.1)