lavfi: loop on request_frame if necessary.

Some filters need several input frames before producing output.
For these filter, it becomes simpler to return 0 in
request_frame() and let the framework call it again until
output has been produced.
lavfi: reindent after last commit.
lavfi/vf_tile: simplify request_frame loop.
lavfi/f_ebur128: remove request_frame hack.
lavfi/af_asetnsamples: simplify request_frame loop.
lavfi/af_atempo: simplify request_frame loop.
lavc: do not init frame with guessed layout.

It is breaking support from files with unknown layout.
Merge remote-tracking branch 'cigaes/master'

* cigaes/master:
  lavc: do not init frame with guessed layout.
  lavfi/af_atempo: simplify request_frame loop.
  lavfi/af_asetnsamples: simplify request_frame loop.
  lavfi/f_ebur128: remove request_frame hack.
  lavfi/vf_tile: simplify request_frame loop.
  lavfi: reindent after last commit.
  lavfi: loop on request_frame if necessary.

Merged-by: Michael Niedermayer <michaelni@gmx.at>
doc/filters: fix error in blend description

Signed-off-by: Paul B Mahol <onemda@gmail.com>
doc/fate.texi: fix typo
matroskadec: fix display_width/height = 0 handling

Fixes Ticket2424

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
Add a work-around for msvc compilation until c99-to-c89 issue 7 is fixed.

Tested-by: Nevcairiel