[m-dev.] For review: Add implementation of reference types (global heap)

[Thomas Charles CONWAY]

Warwick Harvey, you write:
> In order to implement these features, a new memory zone "global heap" was
> added to the runtime system, for a heap which is not reclaimed on failure,
> along with a pair of functions for copying terms to this heap.

Check what just happened to the runtime - all the global stuff like stacks
and heaps have moved into a MercuryEngine data structure. I would
recommend that the global heap become part of the per-engine state so
that locking is not required to allocate from it in the MT case.

Thomas
-- 
Thomas Conway <conway at cs.mu.oz.au>
Nail here [] for new monitor.  )O+