pcm-dvd: Fix 20bit decoding

Increment the pointer as needed.

Bug-Id: 592

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
Merge commit '9880a0d4b131ef36694d62f78060350a81f08b80'

* commit '9880a0d4b131ef36694d62f78060350a81f08b80':
  pcm-dvd: Fix 20bit decoding

See: 5db49fc38d9132e134de92584f296559bec3b789
Merged-by: Michael Niedermayer <michaelni@gmx.at>
libmpcodecs: Fix compilation due to missing static in suncc.

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