motion events relative to the previous mouse position. for
example, if two mouse events arrive, the first at x+1,y and
the second at x+2,y, we used to compute deltas of 1,0 and 2,0
instead of 1,0 and 1,0. that's fixed. also worked around a
bug (probably) in windows that caused a motion event after a
SetCursorPos() to be lost or reported one pixel off from the
correct position. now using mouse_event() which doesn't
have that problem. also fixed calculation of normalized
coordinates for mouse_event() when there are multiple
displays.
a16e7217ce