Optimize division by a constant which is not a power of two

[emilaxelsson]

From the old trac:

Currently we only optimize division by a constant when it is a power of two. This is the simple case; division can be replaced by a right shift. But it is also possible to optimize the general case.

[josefs]

I have some Haskell code which can be used to transform division by a constant into multiplication and addition. It should be fairly straightforward to port it to Feldspar.