Patch courtesy of Codeweavers
Fix mouse movement tracking. For a non-window-related mouse-move event,
calculate the new position by adding the event's delta-x and delta-y values
to the previous mouse position. Do not rely on the current mouse position
because it may have been changed by a XWarpPointer call.
(cherry picked from commit 7a67935b05a475215b9bdbb959e4f7e15f32416f)
0b6e14d46f