MAddXYToParticlesQ CoordinateList.l,NumPoints.l,XToAdd.q,YToAdd.q ; Add constants to all particles

Adds constant value XToAdd.q to X.q in the particle list, and constant value
YToAdd.q to Y.q in the particle list. The constants are added to all particles.
To ignore a component, an adder of 0 is permitted. If either XToAdd or YToAdd are
0, optimised routines will be used.