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

	* 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.