ffmpeg: make reading packets from thread blocking.

If a packet is not ready on the input selected by ffmpeg,
it will read from another input instead. If that happens
repeatedly, frames will accumulate somewhere later in the
processing to ensure streams synchronization. It can happen
in particular when reading from a slow medium or an
expensive lavfi filter graph.

Make reading from normal demuxers on non-streamed data and
from the lavfi pseudo-device blocking to avoid that.

Should fix trac ticket #3079.
build: The MPEG-4 video parser depends on h263dsp

The dependency is indirect through the h263/mpegvideo code.
CC: libav-stable@libav.org
svq3: Adjust #endif comment
bit_depth_template: Use file name as multiple inclusion guard
x86: dsputil: Use correct file name as multiple inclusion guard
avcodec: Consistently name encoder init functions foo_encode_init
mpeg4video_parser: Drop pointless av_-prefix from static function
Merge commit '192ccc5034ad4ac1b5022fc16c1162267add6a0f'

* commit '192ccc5034ad4ac1b5022fc16c1162267add6a0f':
  build: The MPEG-4 video parser depends on h263dsp

Conflicts:
	configure

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit '61e7c7f27b0a2652bf5cd282b97762ee99d025ef'

* commit '61e7c7f27b0a2652bf5cd282b97762ee99d025ef':
  svq3: Adjust #endif comment

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit 'ba42c852477e87f6e47a5587e8f7829c46c52032'

* commit 'ba42c852477e87f6e47a5587e8f7829c46c52032':
  bit_depth_template: Use file name as multiple inclusion guard

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit '017a06a9ee86b047079166c2694c9c655ff03356'

* commit '017a06a9ee86b047079166c2694c9c655ff03356':
  x86: dsputil: Use correct file name as multiple inclusion guard

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit '984e3398662d460e15904f9e4a6df9ef759070cb'

* commit '984e3398662d460e15904f9e4a6df9ef759070cb':
  avcodec: Consistently name encoder init functions foo_encode_init

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge remote-tracking branch 'qatar/master'

* qatar/master:
  mpeg4video_parser: Drop pointless av_-prefix from static function

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge remote-tracking branch 'cigaes/master'

* cigaes/master:
  ffmpeg: make reading packets from thread blocking.

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