Merge commit 'f2143c57'

* commit 'f2143c57':
  vp9: reindent after last commit
  vp9: add frame threading
  vp9: allocate 'b', 'block/uvblock' and 'eob/uveob' dynamically.
  vp9: split last/cur_frame from the reference buffers.

This commit is a noop, we already have all these changes. Again, we will
need in the future to analyse the tiny differences between the two
repository on the vp9 files. But in the current state, it's a real pain
to do at every commit due to the huge differences (such as files split
and cosmetics).
Merged-by: Clément Bœsch <u@pkh.me>