lavc & lavf: replace deprecated av_log* functions

Signed-off-by: Paul B Mahol <onemda@gmail.com>
lavd/lavfi: upgrade to AVFrame.

Fix a memory leak because the compat implementation of
AV_BUFFERSINK_FLAG_PEEK is not identical to the previous one.
dpxenc: fix data offset

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>