[ogg-dev] liboggz: use ogg_int64_t instead of C99 int64_t for the benefit of you-can-guess-who

[ogg.k.ogg.k at googlemail.com]

> Since these are the only two uses of int64_t instead of ogg_int64_t in
> liboggz, please commit.

In svn. Didn't get the OK from Conrad from committing to his software,
hope it's OK kfish ^_^