Revert "twolame: use FL32 as input"

This reverts commit 2363d00e1131bc4b50e3a15a6593e824bee68dd7.

Twolame converts from FL32 to S16 internally anyway so no point
using this instead of converting inside vlc.

Pointed-out-by: Rémi Denis-Courmont
twolame: set pf_encode at the end
faad: set decode_audio at the end
twolame: fix build after revert