droplet is a cloud variable server in C

[GarboMuffin]

It's pretty fast and fixes the backpressure issues that the Node.js server experiences. Multithreading is much more viable, if the need arises.

TODOs for username-validate-prod parity:

• [x] sync username validation
• [ ] async username validation + message replay (does disabling rx on wsi work?)
• [ ] empty room removal
• [x] reject empty user agent
• [x] reject scratch session token cookies
• [x] close codes
• [ ] per message deflate? an optimized L7 protocol might be more viable
• [ ] verify that values are numbers?
• [x] keep alives