This adds an option to enable relative input for the Wiimote IR
as described in issue 9014.
Enabling it will result in the pointer not going back to the centre
and the inputs will control the direction, not the absolute position.
Also adds a Dead Zone setting which is really needed when relative
input is enabled to prevent the cursor from slowly drifting on
most controllers. (Note: the Deadzone setting has no effect when
relative input is disabled)
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