Introduce "available" concept for ports, and communicate that to clients. Bump protocol version to 24.

Note: There is still no notification when status availability changes.

Signed-off-by: David Henningsson <david.henningsson@canonical.com>

src/pulsecore/sink.h

@@ -60,6 +60,7 @@ struct pa_device_port {
     char *description;
 
     unsigned priority;
+    pa_port_available_t available;         /* PA_PORT_AVAILABLE_UNKNOWN, PA_PORT_AVAILABLE_NO or PA_PORT_AVAILABLE_YES */
 
     /* .. followed by some implementation specific data */
 };