[arm] need to cast values to signed for subtractions for proper flag vals
[arm] need to cast values to signed for subtractions for proper flag vals

could have fixed this in utils.py using bitwise magic, but interpretive
pydgin always uses signed int values, so would have needed different impls
for translated and interpretive

futurecore/pydgin,cornell-brg/pydgin,futurecore/pydgin,cornell-brg/pydgin,futurecore/pydgin,cornell-brg/pydgin,cornell-brg/pydgin,futurecore/pydgin