* fcntl.cc (fcntl64): Call pthread_testcancel.

	* fcntl.cc (fcntl64): Call pthread_testcancel.
	* fhandler_socket.cc (fhandler_socket::connect): Ditto.
	(fhandler_socket::accept4): Ditto.
	(fhandler_socket::recvfrom): Ditto.
	(fhandler_socket::recvmsg): Ditto.
	(fhandler_socket::sendto): Ditto.
	(fhandler_socket::sendmsg): Ditto.
	* flock.cc (lf_setlock): Allow to cancel thread running blocking
	file lock.  Try to make code more readable.
	(lockf): Call pthread_testcancel.
	* mmap.cc (msync): Ditto.
	* posix_ipc.cc (ipc_cond_timedwait): Call pthread::static_cancel_self
	rather than pthread_testcancel.
	* select.cc (cygwin_select): Call pthread_testcancel.
	* syscalls.cc (pread): Ditto.
	(pwrite): Ditto.
	(readv): Ditto.
	(writev): Ditto.
	(open): Ditto.
	(close): Ditto.
	(fsync): Ditto.
	* termios.cc (tcdrain): Ditto.
	* thread.cc: Align list of cancellation points with above changes.
	Mark not-implemented functions, too.
	(cancelable_wait): Don't set unused object indices to WAIT_FAILED
	since that could result in wrong behaviour.  Set them to the invalid
	value WAIT_TIMEOUT + 1 instead.