core: Add extended stream API to support compressed formats

This is the beginning of work to support compressed formats natively in
PulseAudio. This adds a pa_stream_new_extended() that takes a format
structure, sends it to the server (=> protocol extension) and has the
server negotiate with the appropropriate sink to figure out what format
it should use.

This is work in progress, and works only with PCM streams. Actual
compressed format support in some sink needs to be implemented, and
extensive testing is required.

More details on how this is supposed to work is available at:
http://pulseaudio.org/wiki/PassthroughSupport

src/pulse/stream.h

@@ -26,6 +26,7 @@
 #include <sys/types.h>
 
 #include <pulse/sample.h>
+#include <pulse/format.h>
 #include <pulse/channelmap.h>
 #include <pulse/volume.h>
 #include <pulse/def.h>
@@ -356,6 +357,16 @@ pa_stream* pa_stream_new_with_proplist(
         const pa_channel_map *map         /**< The desired channel map, or NULL for default */,
         pa_proplist *p                    /**< The initial property list */);
 
+/* Create a new, unconnected stream with the specified name, the set of formats
+ * this client can provide, and an initial list of properties. While
+ * connecting, the server will select the most appropriate format which the
+ * client must then provide. \since 1.0 */
+pa_stream *pa_stream_new_extended(
+        pa_context *c                     /**< The context to create this stream in */,
+        const char *name                  /**< A name for this stream */,
+        pa_format_info * const * formats  /**< The list of formats that can be provided */,
+        pa_proplist *p                    /**< The initial property list */);
+
 /** Decrease the reference counter by one */
 void pa_stream_unref(pa_stream *s);