MediaClient: IDs should be signed integers

* It's very important to use a negative value to identify
non valid or uninitialized connections. Additionally, it's preferred
to don't interfere with media_kit types as long as the framework use
it in the backend.

headers/private/media/experimental/MediaClientDefs.h

@@ -13,10 +13,11 @@
 namespace BPrivate { namespace media {
 
 
-typedef uint64 media_client_id;
+typedef int64 media_client_id;
+typedef int64 media_connection_id;
+
 typedef uint64 media_client_kinds;
 typedef uint64 media_connection_kinds;
-typedef uint64 media_connection_id;
 
 
 enum media_client_kind {

src/kits/media/experimental/MediaClient.cpp

@@ -78,7 +78,7 @@ public:
 BMediaClient::BMediaClient(const char* name,
 	media_type type, media_client_kinds kinds)
 	:
-	fLastID(0)
+	fLastID(-1)
 {
 	CALLED();
 

src/kits/media/experimental/MediaConnection.cpp

@@ -21,7 +21,7 @@ BMediaConnection::BMediaConnection(media_connection_kinds kinds)
 	CALLED();
 
 	fConnection.kinds = kinds;
-	fConnection.id = 0;
+	fConnection.id = -1;
 	//fConnection.client = media_client::null;
 }