avformat: AVMetadataTag and av_metadata_get don't exist anymore
avformat: AVMetadataTag and av_metadata_get don't exist anymore

They were copied verbatim to AVDictionary equivalents some time ago

vlc-mirror/vlc,krichter722/vlc,jomanmuk/vlc-2.2,vlc-mirror/vlc-2.1,vlc-mirror/vlc,shyamalschandra/vlc,xkfz007/vlc,krichter722/vlc,jomanmuk/vlc-2.2,jomanmuk/vlc-2.1,jomanmuk/vlc-2.2,xkfz007/vlc,vlc-mirror/vlc-2.1,xkfz007/vlc,vlc-mirror/vlc,shyamalschandra/vlc,jomanmuk/vlc-2.1,krichter722/vlc,jomanmuk/vlc-2.2,vlc-mirror/vlc-2.1,xkfz007/vlc,jomanmuk/vlc-2.2,krichter722/vlc,krichter722/vlc,jomanmuk/vlc-2.1,jomanmuk/vlc-2.1,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.1,xkfz007/vlc,shyamalschandra/vlc,vlc-mirror/vlc,vlc-mirror/vlc,vlc-mirror/vlc,shyamalschandra/vlc,jomanmuk/vlc-2.2,xkfz007/vlc,vlc-mirror/vlc,jomanmuk/vlc-2.2,vlc-mirror/vlc-2.1,shyamalschandra/vlc,krichter722/vlc,shyamalschandra/vlc,jomanmuk/vlc-2.1,vlc-mirror/vlc-2.1,xkfz007/vlc,krichter722/vlc,shyamalschandra/vlc,jomanmuk/vlc-2.1,vlc-mirror/vlc-2.1