Read the album_artist, grouping and lyrics metadata.

Our muxer writes these out, so we really should support reading them.
Fixes ticket #30.

libavformat/mov.c

@@ -144,9 +144,12 @@ static int mov_read_udta_string(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     case MKTAG(0xa9,'n','a','m'): key = "title";     break;
     case MKTAG(0xa9,'a','u','t'):
     case MKTAG(0xa9,'A','R','T'): key = "artist";    break;
+    case MKTAG( 'a','A','R','T'): key = "album_artist";break;
     case MKTAG(0xa9,'w','r','t'): key = "composer";  break;
     case MKTAG( 'c','p','r','t'):
     case MKTAG(0xa9,'c','p','y'): key = "copyright"; break;
+    case MKTAG(0xa9,'g','r','p'): key = "grouping"; break;
+    case MKTAG(0xa9,'l','y','r'): key = "lyrics"; break;
     case MKTAG(0xa9,'c','m','t'):
     case MKTAG(0xa9,'i','n','f'): key = "comment";   break;
     case MKTAG(0xa9,'a','l','b'): key = "album";     break;