window_center_coord

	WINDOW_CENTER_COORD(window_id)

	This macro returns a screen coordinate value (row or column,
	depending on usage) that will center one window within another.

	window_id	ID of reference window

	This macro is found in: macro_h

	Related macros:

	WINDOW_ABOVE_COORD, WINDOW_BELOW_COORD, WINDOW_ABOVE_OR_BELOW_COORD,
	WINDOW_LEFT_COORD, WINDOW_RIGHT_COORD, WINDOW_LEFT_OR_RIGHT_COORD,
	WINDOW_ALIGN_COORD, WINDOW_ALIGN_CENTER_COORD,
	WINDOW_ALIGN_ABOVE_COORD, WINDOW_ALIGN_BELOW_COORD,
	WINDOW_ALIGN_ABOVE_OR_BELOW_COORD, WINDOW_ALIGN_LEFT_COORD,
	WINDOW_ALIGN_RIGHT_COORD, WINDOW_ALIGN_LEFT_OR_RIGHT_COORD,
	WINDOW_EXTRACT_ID