lua.wetgenes.tardis.m4.get_rotation_q4
q4 = m4:get_rotation_q4(r)
Get quaternion rotation from a scale/rot/trans matrix. Note that scale is assumed to be uniform which it usually is. If that is not the case then remove the scale first.
If r is provided then the result is written into r and returned otherwise a new q4 is created and returned.