transition_mix.c: prevent serializing previous_mix and reset previous_mix on seeking.

[melted] / setenv_mc

# Environment variable settings to allow execution without install

export LD_LIBRARY_PATH=\
`pwd`/../mpeg_sdk_release/bin:\
`pwd`/../dvcpro_sdk_release/lib:\
`pwd`/../sr_sdk_release/lib:\
$LD_LIBRARY_PATH