UintID arith IntID is ambiguous

[mkpellegrino]

It's not clear what type of expression the result should be... A? XA?
if performing: 221 * -10 the result should be in XA as -2210... so that's the two's complement of 2210 as a WORD,
but if performing 7 * -10 the result is the two's complement of 70... that's in A... should we make it a word anyhow? If we do,m then if its cast to a uint... we lose the sign!