[clang-tidy] use default member init

Found with modernize-use-default-member-init

Signed-off-by: Rosen Penev <rosenp@gmail.com>

src/playlist/plugins/AsxPlaylistPlugin.cxx

@@ -40,7 +40,7 @@ struct AsxParser {
 	 */
 	enum {
 		ROOT, ENTRY,
-	} state;
+	} state{ROOT};
 
 	/**
 	 * The current tag within the "entry" element.  This is only
@@ -56,8 +56,7 @@ struct AsxParser {
 
 	TagBuilder tag_builder;
 
-	AsxParser()
-		:state(ROOT) {}
+	AsxParser() = default;
 
 };
 

src/playlist/plugins/PlsPlaylistPlugin.cxx

@@ -57,9 +57,9 @@ ParsePls(TextInputStream &is, std::forward_list<DetachedSong> &songs)
 
 	struct Entry {
 		std::string file, title;
-		int length;
+		int length{-1};
 
-		Entry():length(-1) {}
+		Entry() = default;
 	};
 
 	static constexpr unsigned MAX_ENTRIES = 65536;

src/playlist/plugins/RssPlaylistPlugin.cxx

@@ -40,7 +40,7 @@ struct RssParser {
 	 */
 	enum {
 		ROOT, ITEM,
-	} state;
+	} state{ROOT};
 
 	/**
 	 * The current tag within the "entry" element.  This is only
@@ -57,8 +57,7 @@ struct RssParser {
 
 	TagBuilder tag_builder;
 
-	RssParser()
-		:state(ROOT) {}
+	RssParser() = default;
 };
 
 static void XMLCALL