DecoderPlugin: move functions into the struct

src/TagFile.cxx

@@ -53,8 +53,8 @@ tag_file_scan(const char *path_fs,
 
 	do {
 		/* load file tag */
-		if (decoder_plugin_scan_file(*plugin, path_fs,
-					     handler, handler_ctx))
+		if (plugin->ScanFile(path_fs,
+				     *handler, handler_ctx))
 			break;
 
 		/* fall back to stream tag */
@@ -67,9 +67,8 @@ tag_file_scan(const char *path_fs,
 
 			/* now try the stream_tag() method */
 			if (is != nullptr) {
-				if (decoder_plugin_scan_stream(*plugin, is,
-							       handler,
-							       handler_ctx))
+				if (plugin->ScanStream(*is,
+						       *handler, handler_ctx))
 					break;
 
 				is->LockSeek(0, SEEK_SET, IgnoreError());