To ease changing all the VOs to the new OSD rendering, fallbacks,
conversions, support code etc. was left all over the code. Now that
all VOs have been changed, all that code is inactive. Remove it.
Strip down spudec.c. We don't need the old grayscale and scaling stuff
anymore. (Not removing spudec itself yet - I'm not confident that the
libavcodec DVD sub decoder is sufficient, and it would also require
some hacks to get DVD palette and resolution information from libdvdread
to libavcodec.)
The option --spuaa, --spualign, --spugauss were used with the old sub
scaling code, and don't do anything anymore.
When timestamps jump by more than 30 seconds, assume an unexpected
discontinuity. Fixes encoding aborts (i.e. no more frames written) at
DVD cell switches.