* fhandler.h (fhandler_pty_master::tcgetpgrp): Declare.

* fhandler_termios.cc (fhandler_termios::tcgetpgrp): Only return
	valid pgid if tty is controlling tty.  Set errno to ENOTTY and
	return -1 otherwise.
	(fhandler_pty_master::tcgetpgrp): New function.  Return 0 for
	master side of pty if it's not the controlling tty of the process.

winsup/cygwin/fhandler.h

@@ -1109,6 +1109,7 @@ public:
   int dup (fhandler_base *);
   void fixup_after_fork (HANDLE parent);
   void fixup_after_exec ();
+  int tcgetpgrp ();
 };
 
 class fhandler_tty_master: public fhandler_pty_master