set Sec-WebSocket-Protocol: binary in response if request header
Sec-WebSocket-Protocol: binary provided by client in Upgrade: websocket
request, or if wstunnel.frame-type = "binary" in lighttpd config
centralize most waitpid() handling in core server, with hooks for
modules to be informed of pid and status when a process exits.
This enables faster discovery (and restart) of exited processes,
and also allows for lighttpd to manage backend processes in the
parent (master) process when server.max-worker > 0.
decodes websockets and passes body back and forth from backend
(body could be known protocol such as JSON, or any custom protocol)
originally based off https://github.com/nori0428/mod_websocket