Bugfix: Avoid out of bounds coordinates when moving floating windows (Thanks eeemsi)

Bugfix: Avoid out of bounds coordinates when moving floating windows (Thanks eeemsi)

This commit makes the coordinates proportional when moving floating windows.
That is, if you have a window at the bottom of your 1920 px monitor and move it
to your 800 px monitor, it will be at the bottom of the 800 px monitor (and not
out of bounds).