Replace evws_send with evws_send_text, and introduce new API -
evws_send_binary, that can be used to send binary frames.
But note, that this commit breaks the ABI compatibility, but it should be OK,
since there was only alpha release with evws_send, and nobody should rely on
this, and I hope nobody does (we decided to go this way to avoid supporting
deprecated API).
This adds few functions to use evhttp-based webserver to handle incoming
WebSockets connections. We've tried to use both libevent and libwebsockets in
our application, but found that we need to have different ports at the same
time to handle standard HTTP and WebSockets traffic. This change can help to
stick only with libevent library.
Implementation was inspired by modified Libevent source code in ipush project
[1].
[1]: https://github.com/sqfasd/ipush/tree/master/deps/libevent-2.0.21-stable
Also, WebSocket-based chat server was added as a sample.
