NAME
	GetVPModeID -- get the 32 bit DisplayID from a ViewPort. (V36)

   SYNOPSIS
	modeID =  GetVPModeID( vp )
	d0		       a0

	ULONG GetVPModeID( struct ViewPort *);

   FUNCTION
	returns the normal display modeID, if one is currently  associated
	with this ViewPort.

   INPUTS
	vp -- pointer to a ViewPort structure.

   RESULT

	modeID -- a 32 bit DisplayInfoRecord identifier associated with
		  this ViewPort, or INVALID_ID.

   NOTES
	Test the return value of this function against INVALID_ID, not NULL.
	(INVALID_ID is defined in graphics/displayinfo.h).

   BUGS

   SEE ALSO
	graphics/displayinfo.h, ModeNotAvailable()