This commit adds `projgen`, a very simplistic project generator.
Some knobs to the build system were added to ensure that only the
needed parts will build with each end (building the GMod module won't build projgen
since that isn't needed on the host)
The fun part will be figuring out how to jail things properly
32-bit builds using the development headers work on the legacy 32-bit branch so I don't really see a reason to not support it..
sure, it sucks that I now won't be able to get rid of a pretty gnarly codepath, but /shrug