* cygthread.cc (cygthread::stub): Set inuse to false when exiting.

(cygthread::cygthread): Actually pass name as argument to debugging output to
avoid SEGV when strace'ing.
(cygthread::release): Don't set stack_ptr to NULL, since it is only set once on
first entry to a stub not on each stub iteration.
(cygthead::exit_thread): Remove obsolete function.
* cygthread.h (cygthread::exit_thread): Ditto.

winsup/cygwin/cygthread.h

@@ -41,7 +41,6 @@ class cygthread
   operator HANDLE ();
   void * operator new (size_t);
   static cygthread *freerange ();
-  void exit_thread ();
   static void terminate ();
   bool SetThreadPriority (int nPriority) {return ::SetThreadPriority (h, nPriority);}
   void zap_h ()