Make macOS Compatible

[kdavis-mozilla]

In the process of getting mts to run on macOS I had to make modifications to

1. mts
2. marian-dev
3. ssplit-cpp

in particular I had to fork and then create a branches of these repos and then modify the branches such that all the repos work together. My forks + branches are

1. mts
2. marian-dev
3. ssplit-cpp

Should I just submit PR's to the masters of all the above repos to make mts macOS compatible?