clang-tidy: add explicit deleted constructors

Found with cppcoreguidelines-special-member-functions

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

src/decoder/plugins/MadDecoderPlugin.cxx

@@ -138,6 +138,9 @@ public:
 	MadDecoder(DecoderClient *client, InputStream &input_stream) noexcept;
 	~MadDecoder() noexcept;
 
+	MadDecoder(const MadDecoder &) = delete;
+	MadDecoder &operator=(const MadDecoder &) = delete;
+
 	void RunDecoder() noexcept;
 	bool RunScan(TagHandler &handler) noexcept;
 

src/decoder/plugins/OpusDecoderPlugin.cxx

@@ -137,6 +137,9 @@ public:
 
 	~MPDOpusDecoder();
 
+	MPDOpusDecoder(const MPDOpusDecoder &) = delete;
+	MPDOpusDecoder &operator=(const MPDOpusDecoder &) = delete;
+
 	/**
 	 * Has DecoderClient::Ready() been called yet?
 	 */

src/decoder/plugins/VorbisDecoderPlugin.cxx

@@ -80,6 +80,9 @@ public:
 		DeinitVorbis();
 	}
 
+	VorbisDecoder(const VorbisDecoder &) = delete;
+	VorbisDecoder &operator=(const VorbisDecoder &) = delete;
+
 	bool Seek(uint64_t where_frame);
 
 	static AudioFormat CheckAudioFormat(const vorbis_info &vi) {