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/share/safeproc.c

@@ -123,7 +123,7 @@ struct window_procs safe_procs = {
 #endif
     safe_get_color_string,
 #endif
-    safe_start_screen, safe_end_screen, safe_outrip,
+    safe_outrip,
     safe_preference_update,
     safe_getmsghistory, safe_putmsghistory,
     safe_status_init,
@@ -440,18 +440,6 @@ safe_delay_output(void)
     return;
 }
 
-void
-safe_start_screen(void)
-{
-    return;
-}
-
-void
-safe_end_screen(void)
-{
-    return;
-}
-
 void
 safe_outrip(winid tmpwin UNUSED, int how UNUSED, time_t when UNUSED)
 {