Jp1306 -- Scatter now uses point clipping instead of line clipping

I'm not sure why we even have code for line clipping - must be a remnant from something Skittles was working on.  I grepped it and the only function that calls it is itself.

Anyway I removed some extraneous spaces and added a clipping function that scans per per point. I'm going to be using this function later when I do data clipping, so I might as well implement in now.

This should address the weird behaviour in #1306.