* exceptions.cc (try_to_debug): Fix off-by-one problem when resetting

environment variable after error_start detected.
* fhandler_tty_slave.cc (fhandler_tty_slave::close): Clarify debug message.
* syscalls.cc (setsid): Don't increment usecount here, since it will be
automatically decremented on close.

winsup/cygwin/syscalls.cc

@@ -335,7 +335,7 @@ setsid (void)
 		      myself->pgid, myself->ctty, fhandler_console::open_fhs);
       if (cygheap->ctty)
 	{
-	  if (!--cygheap->ctty->usecount)
+	  if (cygheap->ctty->usecount == 1)
 	    cygheap->ctty->close ();
 	  cygheap->ctty = NULL;
 	}