Adding an arbitrary amount of padding bytes at the end of the
ID3 metadata fixes cover art display for some software (iTunes,
Traktor, Serato, Torq).

For reference (ID3 metadata):

[ Apic frames ]                      -> cover doesn't show up
[ Apic frames, Padding ]             -> ok
[ Apic frames, ID3 frames ]          -> ok
[ ID3 frames, Apic frames ]          -> cover doesn't show up
[ ID3 frames, Apic frames, Padding ] -> ok

When parsing the Xing/Info tag, don't set the bit rate if it's an Info tag.

When parsing the stream, don't override the bit rate if it's already set,
otherwise calculate the mean bit rate from parsed frames. This way, the bit
rate will be set correctly both for CBR and VBR streams.
Signed-off-by: Alexander Kojevnikov <alexander@kojevnikov.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

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

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>