window.i4.v = interrupt_window()

	This routine returns the window ID in which the most recent
	interrupt occurred.  If the window was occluded, a value
	of CBS_WINDOW_OCCLUDED will be returned.

	This function returns status values as follows:

	CBS_WINDOW_OCCLUDED	interrupt was in an occluded window
	otherwise		ID of interrupt window

	This function requires the following include files:

	cbslib_h, acnet_errors_h

	Related functions:

	window_intype, intro_tv_windows

	C/C++ usage:

	int	window;

	window = interrupt_window();