libmodplug: fix sz type

Signed-off-by: Paul B Mahol <onemda@gmail.com>
id3v2enc: chapter support

Signed-off-by: Paul B Mahol <onemda@gmail.com>
md5: avoid unnecessary copying.

Where necessary use memcpy instead.
Thanks to Giorgio Vazzana [mywing81 gmail] for
spotting this loop as the cause for the bad
performance.

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