This only changes the script-layer API, but keeps the std::string host
in the C++ layer's ServerOptions. Mostly because the ixwebsocket library
takes host as std::string. Also, maybe at some point we'd want to
support something scheme-based like unix:///var/run/zeek.sock and placing
that in a string could not be totally wrong.
Add tests for IPV6, too.
I believe there's a bug/usage issue in the websockets library
where during send(), EOF is detected and stored, but the receiving
thread is then discarding the last received frame. Avoid the bug
by replacing the close_socket() implementation of the websockets
library just for that test and leave detecting the EOF condition
to the receiving thread.
