Fixed bug #697722 Assert error / global

Fixed bug #697722  Assert error / global

I had to fish around a lot but Splint now handles thing cleanly if a global is used in a /*@requires isnull ..@*/ or similar clause.

Basically, we just ignore the variable as was the old behavior.  The bug was that llassert were failing.  I think things likely became broken after the code implementing the overloading of the requires keyword was added.