maintenance on toplevel Makefile
testbench: thread: add ``thread_id_validity''

It concerns only the three ranges specified in the KIP, and thread version
numbers. Another one much like it should be written for space IDs.
testbench: generate only global TIDs in ForkServ::new_thread

Rather obvious, but as it's been said: if it ain't been tested, it don't work.
thread: reject local, interrupt, and kernel TIDs in ThreadControl

This applies implicitly to space IDs too, because those are only generated
when spacespec == dest_tid.