cleanup and simplification of the really old h_mgr code.
replace array-of-pages data structure with demand-committed VM => allows simple allocation of new resources without having to search for the first free index. I suspect the cause of multiple reported bugs (refs #860, #899, #915) was a race. Most issues are fixed, but the pool's freelist also needs to be made thread-safe and lock-free. this has performance and 64-bit portability implications, so I'll leave it for later (Pool is due for some serious refactoring anyway).

please post a comment if this or similar issues persist.