fixed mouse x/y position (for pointer class global animations)

This is required in rare cases where the mouse x/y position calculated
from raw values (to apply logical screen size scaling corrections)
does not match the final mouse event x/y position -- this may happen
because the SDL renderer's viewport position is internally represented
as float, but only accessible as integer, which may lead to rounding
errors.

Setting the mouse x/y position for pointer class global animations
from the final mouse event position fixes this problem.