Set constraint set 0 and 1 flags for non-scalable as well

This allows decoders to know that a baseline stream doesn't
contain any of the features that aren't in the constrained
baseline subset.

Set bConstraintSet0Flag if using baseline profile (not using
cabac). Always set bConstraintSet1Flag since we always follow
the restrictions of the main profile.

Review at https://rbcommons.com/s/OpenH264/r/886/.