MWrapYParticles CoordinateList.l,NumPoints.l ; Bring particles in from top/bottom edges

Does the same as MWrapParticles except that only the Y.w or Y.q component of each
particle is wrapped. This means that if a particle goes off the top or bottom
edge of the bitmap or clip window, it will be vertically wrapped around. Note
that there is no routine for Ptr.l particles.