If libevent >= 2.2 is detected during configure and "websocket_port" == 0 in the config file, the libwebsocket implementation is disabled and instead the libevent http server offers the websocket connection. The connection to the websocket is then done with the path "/ws".
The player may emit a listener event when shutting down, and since websockets
didn't remove it's listener callback it would receive an event despite being
deinitialized. This would lead to an invalid read by lws_cancel_service in
listener_cb().
In preparation for the new endpoints the following refactorings where
done in lastfm.c:
- Initialize lastfm.c in main.c instead of on first scrobble attempt
(necessary to retrieve the correct lastfm status)
- Return error messages if login attempt failed
- Add api function for status and logout
- Notify about Last.fm status changes
Unrelated changes in lastfm.c are:
- Refactoring of request_post
- Add request parameters sorted alphabetically and remove calling the
sort method in request_post
