Cursor motion events on windows read the position from GetCursorPos()
which wasn't always the same location stored in `lParam`.
In situations where events were handled immediately this wasn't often a
problem, for heavier scenes or when updates between event handling was
slow - many in-between cursor events would be incorrect.
This behavior dates back to the initial commit, there doesn't seem to be
a good reason not to use the cursor coordinates from the event.
Noticed when investigating T102346.
979b295154