* linux-low.c (linux_remove_process): Remove `detaching'

	* linux-low.c (linux_remove_process): Remove `detaching'
	parameter.  Don't release/detach from thread_db here.
	(linux_kill): Release/detach from thread_db here, ...
	(linux_detach): ... and here, before actually detaching.
	(linux_wait_1): ... and here, when a process exits.
	* thread-db.c (any_thread_of): New.
	(thread_db_free): Switch the current inferior to a thread of the
	passed in process.