go regexp + RE2 DFA port
- The regexp tests pass. Though there may still be uncaught bugs. Let me know if you find any of them! No guarantees!
- regexp/internal/dfa tests are currently failing. I need to fix some thingsn there.
- I've got a small change to the DFA that uses package unsafe and makes matches 2x faster. I'll try to get it up soon.
- A bunch of cleanup needs to be done all over this package.