Constness changes

[melted] / demo / mlt_lcut

inigo \
clip1.dv out=100 \
-track \
-blank 49 \
clip2.dv in=100 \
-transition \
luma in=50 out=55 a_track=0 b_track=1 \
-transition \
mix:1 in=50 out=98 a_track=1 b_track=0 \
-transition \
mix start=1 end=0 in=99 out=100 a_track=1 b_track=0 \
$*