Registers are now just words, with pushing from and moving to
registers with specified subtypes just pushing those types into the
word registers. That means there are 8 word registers which can act
as 16 half word registers, which themselves can act as 64 byte
registers.
Uses some bit hacks to quickly check what data type an opcode may have
by shifting down to units then casting it to a data_type_t.
Not very well tested yet, we'll need to see now.
