[__DJGPP__ >= 2] (dos_direct_output): Faster method of

[__DJGPP__ >= 2] (dos_direct_output): Faster method of
writing characters to the screen.
(SCREEN_SET_CURSOR): Remove.
(IT_display_cursor): New function, to turn the cursor on and off.
(IT_cmgoto): New function, sets the cursor to its final position
whenever frame update is complete.
(internal_terminal_init): Set IT_cmgoto as the hook to be called
when frame is up to date.
(dos_rawgetc): Call IT_cmgoto instead of the SCREEN_SET_CURSOR
macro (which is gone now).
(XMenuActivate): Turn off the cursor while the menu is displayed,
to prevent it from showing through the menu panes.