* xdisp.c (redisplay): Use ! EQ to compare the old and new arrow

* xdisp.c (redisplay): Use ! EQ to compare the old and new arrow
	positions, not !=.
	(mark_window_display_accurate): Barf if WINDOW isn't a window.
	(display_string): Test buffer_defaults.ctl_arrow using NILP,
	instead of comparing it with zero.

	* xdisp.c (last_arrow_position, last_arrow_string): Make these
	static.

	* xdisp.c (message): Re-write this in terms of message1.
	(message1): Move code to clear out echo_area_glyphs and
	previous_echo_glyphs from message to here.