audio output core: normalize tracks without replaygain peak data (fix #8165)

Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>
Drop aborted SNOW codec

This is not supported in libavcodec anymore.
mkv: fix format string
v4l2: update headers (refs #5474)
vorbis demux: convert generic field names to uppercase (fix #8105)

Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>
macosx: don't overwrite existing files on stream-output (close #7752)
v4l2: use buffer PTS where available (fix #5474)
macosx: use UTF-8 instead of Windows Latin 1 as source code encoding
Revert "aout: make log message to be debug as there isn't any real error if no filters needed"

If the user explicitly asks for a filter, it's an error to not be able
to instatiate it.
This reverts commit 7b0761c4359d12de0bad78a1d255a55cb89bc562.
avcodec: update to audio4 decoding API

Note that the input coded buffer is now only freed if the decoding
returns a decoded frame, or the buffer has been entirely consumed
(see *pp_block = NULL).
avcodec: cosmetics
avcodec: zero copy audio decoding
Remove unsupported SONIC codec
avcodec: remove obsolete compatibility stuff
avcodec: require version 24.25.0 or later
contrib: ffmpeg: update required versions
avcodec: remove support for old versions
avcodec: replace gone CODEC_ID_* with AV_CODEC_ID_*

This is necessary to compile with libav.git HEAD or with contribs.
Streaming output still needs fixing.
avcodec: allow compilation with lavc 55
stats: eliminate useless CloseDecoder callback