Merge commit 'ed7922faac4ea4c893efc3cdf8102ebc49fcc011'

* commit 'ed7922faac4ea4c893efc3cdf8102ebc49fcc011':
  mux: drop one of the hacks comprising compute_pkt_fields2()

Conflicts:
	libavformat/mux.c

Not merged as -async drop / -vsync drop depends on this code

Merged-by: Michael Niedermayer <michaelni@gmx.at>