ADDED: Limit the program space usage per module.  See set_module/1 and
module_property/1.
WIP to enforce program space limit for creating predicates.  This is a bit
too hard as it implies that lookupProcedure() can return NULL, while a lot
of code assumes it can't.  Added quite a few tests, but I consider the risc
of regression too large to persue.
Updated pengines.
Suppress `Reachable from' if there is no context.