New Features

• --once option: accept only one client and exit on disconnection
• --readonly option: do not allow clients to write to the TTY
• --check-origin option: do not allow websocket connection from different origin
• HTTP Server header changed to ttyd, eg: ttyd/1.1.0 (libwebsockets/2.0.2)

Improvements

• Added check for lws_config.h, some version of libwebsockets may not have this header file
• libwebsockets : handle fragmented messages, this allows large input on the web
• OpenWrt Makefile: changed the openssl dependency to libopenssl