While implementing some more mnemonics and testing
them, it was clear that modrm parsing was wrong.
Now reg to reg and immediates, together with
GPR1 interpretation should work as expected.
GPR1 interpretation can currently not be merged
into the modrm function, as with the current
abstraction the REG needs to select the correct
mnemonic, for which we need to also know the second
operand, which will only be parsed afterwards.
But this will be incorporated at some point, this
just marks the first working state.
