* handle socket options for UNIX socket same as others
* set FD_CLOEXEC by default
* invoke `socket_options` callback if set
* Offer Client info even on UNIX socket based Server
HTTP Request header "REMOTE_PORT" contains client process id if possible
when Server works on UNIX socket.
* retrigger checks
* retrigger checks
* add support macOS
Co-authored-by: Changbin Park <changbin.park@ahnlab.com>