pgsql: Actually ...

Log Message:
-----------
Actually ... it's pretty silly that parse_oper.c doesn't set up the
opfuncid of an OpExpr initially, considering that it has the information
at hand already.  We'll still treat opfuncid as a cache rather than a
guaranteed-valid value, but this change saves one more syscache lookup
in the normal code path.

Modified Files:
--------------
    pgsql/src/backend/parser:
        parse_oper.c (r1.97 -> r1.98)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/parse_oper.c?r1=1.97&r2=1.98)
    pgsql/src/include/nodes:
        primnodes.h (r1.135 -> r1.136)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/nodes/primnodes.h?r1=1.135&r2=1.136)