Temporary kluge to let RI triggers work on tables outside the system

Temporary kluge to let RI triggers work on tables outside the system
catalog namespace.  This will not do as a production solution because
the interpretation of RI trigger arguments will vary depending on the
current namespace search path.  I'm just putting it in so that the RI
regression tests don't fail while schema development proceeds.  We
must find a better answer before 7.3 can be released.