Support for ProxyProtocol

[mkykadir]

There might be some configuration scenarios where Vibe is placed behind a reverse proxy or a load balancer. Applications cannot know actual peer address connecting through proxy without special protocols. There is a protocol called Proxy Protocol which tries to solve that problem by adding a header to TCP/UDP stream data. Vibe.d can parse those headers when configured and can provide actual peer address to applications.

Implementing this protocol might also drop the need of this