Convert to using pa_socket_client rather than using blocking IO.

Convert to using pa_socket_client rather than using blocking IO.

This change requires a reference to the mainloop api be passed during initial connection.
In addition, the passing in of the session id during connect has been deprecated. A new function pa_rtsp_set_url has been added to allow the URL to be set by external code. The concept of sid is something specific to raop, not to the rtsp client.

git-svn-id: file:///home/lennart/svn/public/pulseaudio/branches/coling@2360 fefdeb5f-60dc-0310-8127-8f9354f1896f