window-port updates

Remove start_screen() and end_screen() from the
Window-port interface.

They were only ever used by tty, and there was a comment
carried to several window-ports about how they "really
should go away. They are tty-specific"

term_start_screen() and term_end_screen() are part of
terminal/NO_TERMS supporting routines now.

win/X11/winX.c

@@ -146,8 +146,6 @@ struct window_procs X11_procs = {
 #ifdef CHANGE_COLOR /* only a Mac option currently */
     donull, donull,
 #endif
-    /* other defs that really should go away (they're tty specific) */
-    X11_start_screen, X11_end_screen,
 #ifdef GRAPHIC_TOMBSTONE
     X11_outrip,
 #else
@@ -1396,20 +1394,6 @@ X11_number_pad(int state) /* called from options.c */
     return;
 }
 
-/* called from setftty() in unixtty.c */
-void
-X11_start_screen(void)
-{
-    return;
-}
-
-/* called from settty() in unixtty.c */
-void
-X11_end_screen(void)
-{
-    return;
-}
-
 #ifdef GRAPHIC_TOMBSTONE
 void
 X11_outrip(winid window, int how, time_t when)