pgsql: When you do "ARRAY[...]::domain", where domain is a domain over

Log Message:
-----------
When you do "ARRAY[...]::domain", where domain is a domain over an array type,
we need to check domain constraints. We used to do it correctly, but 8.4
introduced a separate code path for the "ARRAY[]::arraytype" case to infer
the type of an empty ARRAY construct from the cast target, and forgot to take
domains into account.

Per report from Florian G. Pflug.

Modified Files:
--------------
    pgsql/src/backend/parser:
        parse_expr.c (r1.248 -> r1.249)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/parse_expr.c?r1=1.248&r2=1.249)