Add support for the OriginalDate tag

See https://picard.musicbrainz.org/docs/mappings/

This tag is useful when the user would like all releases of the same
album to be sorted next to each other.

src/db/plugins/ProxyDatabasePlugin.cxx

@@ -158,6 +158,9 @@ static constexpr struct {
 	{ TAG_NAME, MPD_TAG_NAME },
 	{ TAG_GENRE, MPD_TAG_GENRE },
 	{ TAG_DATE, MPD_TAG_DATE },
+#if LIBMPDCLIENT_CHECK_VERSION(2,12,0)
+	{ TAG_ORIGINAL_DATE, MPD_TAG_ORIGINAL_DATE },
+#endif
 	{ TAG_COMPOSER, MPD_TAG_COMPOSER },
 	{ TAG_PERFORMER, MPD_TAG_PERFORMER },
 	{ TAG_COMMENT, MPD_TAG_COMMENT },

src/output/plugins/HaikuOutputPlugin.cxx

@@ -395,6 +395,7 @@ HaikuOutput::SendTag(const Tag &tag)
 			break;
 		case TAG_GENRE:
 		case TAG_DATE:
+		case TAG_ORIGINAL_DATE:
 		case TAG_PERFORMER:
 		case TAG_COMMENT:
 		case TAG_DISC:

src/tag/Id3Scan.cxx

@@ -55,6 +55,10 @@
 #define ID3_FRAME_ALBUM_ARTIST "TPE2"
 #endif
 
+#ifndef ID3_FRAME_ORIGINAL_RELEASE_DATE
+#define ID3_FRAME_ORIGINAL_RELEASE_DATE "TDOR"
+#endif
+
 gcc_pure
 static id3_utf8_t *
 tag_id3_getstring(const struct id3_frame *frame, unsigned i)
@@ -317,6 +321,8 @@ scan_id3_tag(struct id3_tag *tag,
 			    handler, handler_ctx);
 	tag_id3_import_text(tag, ID3_FRAME_YEAR, TAG_DATE,
 			    handler, handler_ctx);
+	tag_id3_import_text(tag, ID3_FRAME_ORIGINAL_RELEASE_DATE, TAG_ORIGINAL_DATE,
+			    handler, handler_ctx);
 	tag_id3_import_text(tag, ID3_FRAME_GENRE, TAG_GENRE,
 			    handler, handler_ctx);
 	tag_id3_import_text(tag, ID3_FRAME_COMPOSER, TAG_COMPOSER,

src/tag/Names.c

@@ -32,6 +32,7 @@ const char *const tag_item_names[TAG_NUM_OF_ITEM_TYPES] = {
 	[TAG_NAME] = "Name",
 	[TAG_GENRE] = "Genre",
 	[TAG_DATE] = "Date",
+	[TAG_ORIGINAL_DATE] = "OriginalDate",
 	[TAG_COMPOSER] = "Composer",
 	[TAG_PERFORMER] = "Performer",
 	[TAG_COMMENT] = "Comment",

src/tag/Type.h

@@ -46,6 +46,7 @@ enum TagType
 	TAG_NAME,
 	TAG_GENRE,
 	TAG_DATE,
+	TAG_ORIGINAL_DATE,
 	TAG_COMPOSER,
 	TAG_PERFORMER,
 	TAG_COMMENT,