sink, source: Support creating suspended sinks and sources

The initial state of a sink or source might not necessarily be IDLE,
because sometimes it might be suspended from the very beginning.

src/pulsecore/source.h

@@ -265,6 +265,8 @@ typedef enum pa_source_message {
 } pa_source_message_t;
 
 typedef struct pa_source_new_data {
+    pa_suspend_cause_t suspend_cause;
+
     char *name;
     pa_proplist *proplist;