* thread.cc (pthread::pthread): Drop setting parent_tls. Call

sigprocmask to copy parent thread signal mask into new parent_sigmask
	member.
	(pthread::thread_init_wrapper): Copy _my_tls.sigmask from new
	parent_sigmask member.
	* thread.h (class pthread): Drop parent_tls.  Add parent_sigmask.

winsup/cygwin/thread.h

@@ -444,7 +444,7 @@ private:
   DWORD thread_id;
   __pthread_cleanup_handler *cleanup_stack;
   pthread_mutex mutex;
-  _cygtls *parent_tls;
+  sigset_t parent_sigmask;
 
   void suspend_except_self ();
   void resume ();