Spring RTS Engine

I've an old work machine that's not being used and has been wiped to factory settings, sitting unused.

If it will help, I can set it up for remote SSH if an engine dev wants to test things on a Mac?

it's a 2016 MBP 13" with maxed out specs, sadly no internal GPU but it should be able to run spring. Let em know if anybody is interested

as we currently have an osx buildslave: https://buildbot.springrts.com/builders/full-macosx this doesn't help this much...

pull requests with fixes are needed