(cygthread::cygthread): Ditto.
(cygthread::terminate_thread): Ditto. Move inuse test earlier or suffer
infinite loop.
* pinfo.cc (_pinfo::dup_proc_pipe): Close handle if DuplicateHandle fails and
process no longer exists.
* spawn.cc (spawn_guts): Create process in suspended state if OS demands it.
* wincap.cc: Add "start_proc_suspended" throughout.
* wincap.h (wincaps): Ditto.
(wincapc): Ditto.