Feersum-1.506_06

Changes for version 1.506_06

multi-server: per-server struct with multi-listener support
new_instance() for multiple independent server instances
tls 1.3 via vendored picotls + openssl
per-listener tls contexts, mixed plain/tls listeners
alpn negotiation for h2/http1.1
http/2 via nghttp2: stream multiplexing, streaming responses, request body with flow control
extended CONNECT / websocket tunnels (rfc 8441)
h2 idle timeout with goaway
runner: multiple --listen, --tls-cert-file, --tls-key-file, --h2, --proxy-protocol, fractional --read-timeout
optimize psgi env hash creation: direct build
header_timeout for slowloris attack protection
max_connections limit for connection-based dos protection
pause_accept/resume_accept for traffic control
active_conns() and total_requests() for monitoring
native io() and return_from_io() for protocol upgrades
query() method for direct query string access
ipv6 support with bracket notation parsing
libev priority controls (read/write/accept_priority)
epollexclusive support for linux prefork scaling
max_accept_per_loop to prevent accept starvation
expect: 100-continue support for http/1.1 clients
transfer-encoding: chunked request body support
poll_cb support on reader handles for streaming input
sendfile() zero-copy file transfer (linux)
so_reuseport for better prefork scaling