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.

outdated/sys/mac/mttymain.c

@@ -581,13 +581,13 @@ tty_number_pad(int arg)
 }
 
 void
-tty_start_screen(void)
+term_start_screen(void)
 {
     iflags.cbreak = 1;
 }
 
 void
-tty_end_screen(void)
+term_end_screen(void)
 {
 }