Fixes bug 208

UnitDieBState is expecting units to be turning, collapsing, or standing.
If a unit is facing direction 3 then it does not turn for a death
animation so the unit keeps its current state; if this state is a non
standing state then UnitDieBState::think() cannot end so the game hangs.

Fix it so that all non collapsing and non turning units are treated as
dying.
Ensure dead and unconscious units do not fall
Merge pull request #592 from cfailde/bug208

Fixes bug 208