decoder/sidplay: read the "date" tag

NEWS

@@ -5,6 +5,7 @@ ver 0.19.18 (not yet released)
   - ffmpeg: support FFmpeg 3.1
   - sidplay: detect libsidplay2 with pkg-config
   - sidplay: log detailed error message
+  - sidplay: read the "date" tag
 * output
   - shout: recognize setting "encoder" instead of "encoding"
 * require gcc 4.7 or newer

src/decoder/plugins/SidplayDecoderPlugin.cxx

@@ -327,6 +327,12 @@ sidplay_scan_file(Path path_fs,
 		tag_handler_invoke_tag(handler, handler_ctx, TAG_ARTIST,
 				       artist);
 
+	/* date */
+	const char *date = GetInfoString(info, 2);
+	if (date != nullptr)
+		tag_handler_invoke_tag(handler, handler_ctx, TAG_DATE,
+				       date);
+
 	/* track */
 	char track[16];
 	sprintf(track, "%d", song_num);