* thread.h (class pthread): Add bool member canceled.

* thread.cc (pthread::pthread): Initialize canceled to false.
	(pthread::cancel): Set canceled before setting cancel_event.
	(pthread::testcancel): Check for canceled.  Only wait for cancel_event
	if canceled is true.  Explain why.
	(pthread::_fixup_after_fork): Set canceled to false.

winsup/cygwin/thread.h

@@ -366,6 +366,7 @@ public:
   void *return_ptr;
   bool valid;
   bool suspended;
+  bool canceled;
   int cancelstate, canceltype;
   _cygtls *cygtls;
   HANDLE cancel_event;