By switching to ff_init_vlc_from_lengths() one can apply both positive
as well as negative offsets for free; in this case it even saves space
because one replaces codes tables that don't fit into an uint8_t by
symbols tables that fit into an uint8_t or can even be completely
avoided as they are trivial.
Signed-off-by: NAndreas Rheinhardt <andreas.rheinhardt@gmail.com>