MWrapParticles CoordinateList.l,NumPoints.l ; Bring particles in from opposite edge to which they left

Checks the particles in the list of X.w,Y.w coordinates as pointed to by
CoordinateList.l to see if they are outside of the bitmap or clip window
dimensions, and if so it makes the particle re-enter at the opposite edge to
which it left. This feature only works within reason, in that the zone of
detection around the edge of the bitmap or clip window is the same width as the
bitmap or clip window itself. Particles further away than that will not be
properly wrapped. An example is that a pixel may leave the bottom of the bitmap,
the wrap will detect this and subtract the height of the bitmap from the Y
coordinate, so that the pixel appears to have re-entered at the top.