* fhandler.h (line_edit_status): Add a new element.

* fhandler_termios.cc (fhandler_termios::line_edit): After accept_input, handle
both potential error condition and pipe full conditions.
* fhandler_tty.cc (fhandler_pty_master::accept_input): Return -1 on error.
(fhandler_pty_master::write): Handle pipe full condition.

winsup/cygwin/fhandler.h

@@ -123,7 +123,8 @@ enum line_edit_status
   line_edit_signalled = -1,
   line_edit_ok = 0,
   line_edit_input_done = 1,
-  line_edit_error = 2
+  line_edit_error = 2,
+  line_edit_pipe_full = 3
 };
 
 enum bg_check_types