lavc: give a typedeffed name to the AVPacket.side_data struct
lavf: add an AVStream field for exporting stream-global side data
Add replaygain side data type and code for parsing replaygain tags.
libavcodec: when decoding, copy replaygain side data to decoded frames
avconv: add stream-global side data to the first demuxed packet
frame: add a function for removing side data from a frame
af_volume: support using replaygain frame side data
mp3dec: export replaygain tags from ID3v2