x11 Double Click inconsistent because of zero movement threshold

[Cammymoop]

LAF implements double click itself on x11 but it has no movement threshold, which causes dropping a lot of intended double clicks due to small mouse movements between the first and second click.

I noticed this when switching to linux and using aseprite after being on windows for awhile, using double click to select tile-wise was only working 50% of the time or less.

It should accumulate movement delta values until a threshold is reached before dropping the pending double click state. (a few pixels of screenspace should be a reasonable default I think Windows defaults to 4 horizontally and vertically counted separately)