libobs: Add private data to definition structures

This is useful for allowing the ability to have private data associated
with the object type definition structures.  This private data can be
useful for things like plugin wrappers for other languages, or providing
dynamically generated object types.

libobs/obs-encoder.h

@@ -223,6 +223,9 @@ struct obs_encoder_info {
 	 * @param[in/out]  info  Video format information
 	 */
 	void (*get_video_info)(void *data, struct video_scale_info *info);
+
+	void *type_data;
+	void (*free_type_data)(void *type_data);
 };
 
 EXPORT void obs_register_encoder_s(const struct obs_encoder_info *info,