[MSDOS]: Include msdos.h.

[MSDOS]: Include msdos.h.
(init_tty) [MSDOS]: Reuse most of WINDOWSNT branch.  Change cpp conditional
to DOS_NT.  Allow only one call to this function in a session.  Don't
allocate a new struct tty_display_info; instead, reuse the_only_display_info.
Call get_tty_size to get screen dimensions.  Call init_baud_rate to set
bad_rate.
(dissociate_if_controlling_tty) [MSDOS]: Ifdef away function body.
(Fsuspend_tty) [MSDOS]: Don't close input and output.
(Fresume_tty) [MSDOS]: Don't reopen the TTY; instead, use stdin/stdout.
(get_tty_terminal, get_named_tty, Ftty_type)
(Fcontrolling_tty_p): Handle output_msdos_raw in addition to output_termcap.
(Fresume_tty, Fsuspend_tty, init_tty, delete_tty): Call
add_keyboard_wait_descriptor and delete_keyboard_wait_descriptor only when
subprocesses are supported