If the destination movie uses a palette cast member in the same location
as the source, but with different data; Director will assume that the old
palette is correct right up until it has to switch to something else via
the score.
Additionally, ensure that all palettes are loaded into the index when
the Cast is loaded, not just single ones that haven't been loaded before.
Fixes movie transitions and palette rendering in Phibos: Following the Comet.
da06ecad9b