Reworked AC3 decoder. No seeking yet but at least we do not need ac3parse anymore.

Reworked AC3 decoder. No seeking yet but at least we do not need ac3parse anymore.

Original commit message from CVS:
Reworked AC3 decoder. No seeking yet but at least we do not need ac3parse
anymore.
Reworked dvdsrc to read scrambled data (DeCSS not included). I have
modified DeCSS a bit to work in GStreamer. Can I release the code or is
there some lawyer that's going to sue me?
MPEG2 SSE motion compensation.
Tried to add PTS to the MPEG decoder but failed.