[theora] Indexing Ogg files for faster seeking

[Christopher Blizzard]

Hey, one thought.  The introduction of an index is great but I think 
that I'm echoing some concerns here that I heard at OVA.  Namely that 
formats that add an index often find players get lazy and won't work 
without them.

We need to make sure we have a solid and unified test suite here so that 
people can test against all these variants.  I understand that j^ has a 
set and other people have stuff in other places.  Or am I mistaken?

--Chris