Remove mtwist library in favor of c++ <random> library.

The included mtwist library always returns 0 when using genrand_int32()
despite being initialized - its function also doesn't seem to return
anything? I don't know enough about random number generation to
attempt to fix it.
Massive commit containing complete rewrite.

I may have gotten a little bit lazy with Git lately. Now that I actually
kind of know what I'm doing, I rewrote/reorganized so much without
committing that it's just easier to lump it together. Server can
send/receive correctly and process client responses but still needs
to handle client disconnects.