Chez Scheme: record large allocations more eagerly for GC trigger
Chez Scheme: record large allocations more eagerly for GC trigger

Although `bytes-allocated` would report just-allocated large chunks,
the check used to trigger a garbage collection uses a lazier
approximation, and so it could wait too longer to tigger a collection
if the lazy part was too large.

mflatt/ChezScheme,mflatt/ChezScheme,mflatt/ChezScheme