hi lo implementation

[SebastienBrand]

Request Description
When either mul or div are called, I would want the hi and lo "registers" to be used to store the requisite information
ex: mul output input1 input2 will put the lower 32 bits of the product in output and in lo and the upper 32 bits in hi
ex: div output input1 input2 will put the quotient in output and lo, and the remainder in hi