Implement more multiplication with ADX instructions

[albinahlback]

Both squaring and multiplication can have higher cases.

For squaring we have $(a_1 B + a_0)^2 = a_1^2 B^2 + 2 a_0 a_1 B + a_0^2$. Compute $a_1^2 B^2$ into result, then compute $a_0^2$ and $2 a_0 a_1 B$ simultaneously and add onto result.

For multiplication, a similar strategy could be used.