How to create your own `consts.jl` file manually

As a tangent to #574, I am wondering how to go about when trying to create your own constants file manually, i.e., one that could live along the others in [`src/consts`](https://github.com/JuliaParallel/MPI.jl/blob/master/src/consts)? Would it be ok to just copy one file, e.g., the one for [OpenMPI](https://github.com/JuliaParallel/MPI.jl/blob/master/src/consts/openmpi.jl) and look at my own MPI implementations `mpi.h` and change everything that is different? Or how would I go about this properly?

Also, regarding proprietary MPI implementations: Does anyone know if this potentially touches copyright issues if I create such a file and provide it publicly, or is it kosher because it only describes the API/ABI and nothing else?