* fhandler.h (fhandler_pty_common::bytes_available): Declare new function.

* fhandler.h (fhandler_pty_common::bytes_available): Declare new function.
(fhandler_pty_master::flush_to_slave): Ditto.
* fhandler_tty.cc (bytes_available): Define new function.
(fhandler_pty_common::bytes_available): Ditto.
(handler_pty_master::flush_to_slave): Ditto.
(fhandler_pty_master::process_slave_output): Call flush_to_slave () here.  Use
bytes_available () rather than PeekNamedPipe.  Cleanup sloppy logic.
(fhandler_pty_slave::read): Use bytes_available () rather than PeekNamedPipe.
(fhandler_pty_slave::ioctl): Ditto.
(fhandler_pty_master::ioctl): Ditto.
(fhandler_pty_master::cleanup): Remove ancient #if 0.
* select.cc (peek_pipe): Call flush_to_slave whenever we're checking for a pty
master.