[arm] add sign_extend_half and sign_extend_byte
[arm] add sign_extend_half and sign_extend_byte

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