* cygthread.cc (cygthread::stub): Don't create an event for "cygself" threads.

Assume that they exit via an ExitThread call.
* cygthread.h (cygthread::SetThreadPriority): New function.
(cygthread::zap_h): New function.
* dcrt0.cc (do_exit): Move cygthread::terminate earlier and establish
exit_state guard.
* fhandler.h (fhandler_tty_master::output_thread): Delete.
* fhandler_tty.cc (fhandler_tty_master::init): Set priority for threads via
method.  Zap handles when done.  Don't treat process_output specially.
(process_output): Call ExitThread directly.
(fhandler_tty_master::fixup_after_fork): Don't worry about output_thread.
(fhandler_tty_master::fixup_after_exec): Ditto.
* sigproc.cc (proc_terminate): Don't detach from hwait_subproc.  Just let it
exit.
(sigproc_init): Close thread handle after initialization.
(wait_sig): Use GetCurrentThread() as SetThreadPriority call rather than
*event* handle.  Call ExitThread directly on termination.
(wait_subproc): Call ExitThread directly on termination.
* tty.cc (tty_list::terminate): Don't attempt t detach from output_thread.

winsup/cygwin/dcrt0.cc

@@ -947,9 +947,10 @@ __main (void)
 
 enum
   {
-    ES_SIGNAL = 1,
-    ES_CLOSEALL = 2,
-    ES_SIGPROCTERMINATE = 3
+    ES_THREADTERM = 1,
+    ES_SIGNAL = 2,
+    ES_CLOSEALL = 3,
+    ES_SIGPROCTERMINATE = 4
   };
 
 extern "C" void __stdcall
@@ -962,6 +963,12 @@ do_exit (int status)
     system_printf ("DisableThreadLibraryCalls (%p) failed, %E",
 		   cygwin_hmodule);
 
+  if (exit_state < ES_THREADTERM)
+    {
+      exit_state = ES_THREADTERM;
+      cygthread::terminate ();
+    }
+
   syscall_printf ("do_exit (%d)", n);
 
   vfork_save *vf = vfork_storage.val ();
@@ -1028,7 +1035,6 @@ do_exit (int status)
   window_terminate ();
   events_terminate ();
   shared_terminate ();
-  cygthread::terminate ();
 
   minimal_printf ("winpid %d, exit %d", GetCurrentProcessId (), n);
   myself->exit (n);