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outdated/sys/wince/winMS.h

@@ -152,8 +152,6 @@ void mswin_number_pad(int state);
 void mswin_delay_output(void);
 void mswin_change_color(void);
 char *mswin_get_color_string(void);
-void mswin_start_screen(void);
-void mswin_end_screen(void);
 void mswin_outrip(winid wid, int how, time_t when);
 void mswin_preference_update(const char *pref);