Implement SYSREF - structural reference counting, allocation, and sysid
management subsystem.
* Structural reference count management, including creation and termination
sequencing (e.g. where the structure might be temporarily referenced
during termination).
* Allocation. It uses an objcache backend for optimal allocation,
deallocation, and memory recovery.
* Sysid assignment and red-black tree indexing. It does this in the
objcache CTOR and DTOR so it costs us absolutely nothing in the
resource allocation / deallocation critical path. sysids will be
reused unless they are externally accessed.