Implement Oshrximm

[ymherklotz]

Currently Oshrximm is not implemented, as it needs to be implemented with a division.

One reason for the mismatch between division and shift is shown below:

-11 / (1 << 1) = -5
-11 >>> 1      = -6

Therefore it will always be more efficient to use unsigned division by a constant compared to signed division by a constant.

Maybe there is a more efficient implementation of this special case.

[ymherklotz]

The following might be the correct, efficient implementation of Oshrximm (x / (2 ^ y)):

q = $signed(x) < 0 ? - ((-x) >> y) : x >> y;