Merge branch 'refs/heads/t/ogg_afh'

Merge branch 'refs/heads/t/ogg_afh'

A patch which teaches the ogg/* audio format handlers to report the
correct length for files with holes. A bug was found in that patch
after the branch had been merged to next, so there's a fixup commit
on top.

The second patch in this series fixes an issue with
ogg_page_granulepos() that can result in incorrect estimates for the
duration of files that use the ogg container format.

Cooking for a year.

* refs/heads/t/ogg_afh:
  ogg_afh_common.c: Check return value of ogg_page_granulepos().
  ogg_afh_common: Fix signedness issue.
  ogg: Detect missing ogg pages.