current meta key mode.
* fhandler_console.cc (fhandler_console::read): Set the top bit of
the character if metabit is true.
* fhandler_console.cc (fhandler_console::ioctl): Implement
KDGKBMETA and KDSKBMETA commands.
* fhandler_tty.cc (process_ioctl): Support KDSKBMETA.
(fhandler_tty_slave::ioctl): Send KDGKBMETA and KDSKBMETA to the
master.
* include/cygwin/kd.h: New file for the meta key mode.
* include/sys/kd.h: New file.
