* cygheap.cc (init_cygheap::init_tls_list): Accommodate threadlist

having a new type threadlist_t *.  Convert commented out code into an
	#if 0.  Create thread mutex.  Explain why.
	(init_cygheap::remove_tls): Drop timeout value.  Always wait infinitely
	for tls_sentry.  Return mutex HANDLE of just deleted threadlist entry.
	(init_cygheap::find_tls): New implementation taking tls pointer as
	search parameter.  Return threadlist_t *.
	(init_cygheap::find_tls): Return threadlist_t *.  Define ix as auto
	variable.  Drop exception handling since crash must be made impossible
	due to correct synchronization.  Return with locked mutex.
	* cygheap.h (struct threadlist_t): Define.
	(struct init_cygheap): Convert threadlist to threadlist_t type.
	(init_cygheap::remove_tls): Align declaration to above change.
	(init_cygheap::find_tls): Ditto.
	(init_cygheap::unlock_tls): Define.
	* cygtls.cc (_cygtls::remove): Unlock and close mutex when finishing.
	* exceptions.cc (sigpacket::process): Lock _cygtls area of thread before
	accessing it.
	* fhandler_termios.cc (fhandler_termios::bg_check): Ditto.
	* sigproc.cc (sig_send): Ditto.
	* thread.cc (pthread::exit): Ditto.  Add comment.
	(pthread::cancel): Ditto.

winsup/cygwin/cygtls.cc

@@ -180,7 +180,7 @@ _cygtls::remove (DWORD wait)
 
   debug_printf ("wait %u", wait);
 
-  cygheap->remove_tls (this, INFINITE);
+  HANDLE mutex = cygheap->remove_tls (this);
   remove_wq (wait);
 
   /* FIXME: Need some sort of atthreadexit function to allow things like
@@ -211,6 +211,11 @@ _cygtls::remove (DWORD wait)
   /* Close timer handle. */
   if (locals.cw_timer)
     NtClose (locals.cw_timer);
+  if (mutex)
+    {
+      ReleaseMutex (mutex);
+      CloseHandle (mutex);
+    }
 }
 
 #ifdef __x86_64__