First set of refactoring MR

This is an initial refactoring of some obvious stuff I've found on orc. I took the liberty to create a ROADMAP.md with the things I've found but I'm sure others like @amyspark would have a list plenty of them. The most relevant part here is the reduction of code for x86 based targets and an initial isolation of functions <-> headers. Given that a new release will be done, this can be delayed safely.

PS. It is better to review this by commit, it might be difficult as a full change set