Currently overHeadText is displayed in a box which
starts at a fixed offset above the base of an actor,
and drops down. This patch changes it to be displayed
at the bottom of a box which goes upwards, offset by
the height of the first frame of the actor's current
animation. It should therefore always end just above
the top of the actor.
This prevents part of the golem's speech being obscured
in the SoA opening cutscene.