'off-heap' resource management.  Default management is stack based management but gc
or a combination of the two is possible.  To declare a stack region use
stack-resource-context.  No matter how the context unwinds, stack resources declared
within will be released.

More options for stack based resources available at tech.resource.stack.

For GC resources, users must not reference the tracked object in the dispose function
else the circular dependency will keep the object in the gc's live set

System for using both weak and soft references generically.  Weak references don't
count for anything in the gc while soft references will keep their object alive as
long as there is no gc pressure.

Implementation of stack based resource system.  Simple, predictable, deterministic,
and applicable to most problems.  Resource contexts are sequences of resources that
need to be, at some point, released.