configure: Only run gas checks on ARM and PowerPC

Standalone GNU assembly is not used on x86.
configure: Check if libwebp compilation will succeed.
Autodetect webp files.
avformat/mov: Support reading Avid's metadata for DNXHD codec.

The AALP atom is necessary to properly decode the alpha channel.
Needed for ticket #3707

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avfilter/showcqt: add and extend tlength and volume options

Add a tlength option with frequency and timeclamp variable

Add to the volume option support for frequency and timeclamp variable,
   a_weighting, b_weighting and c_weighting functions

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avfilter/dctdnoiz: make color [de]correlation less clumsy

This has no impact on overall performance, since the block DCT taking
most of the time anyway.
avfilter/dctdnoiz: remove forward declarations after previous commit
avfilter/dctdnoiz: use 32-bit (float) operations instead of 64 (double) for DCTs

This makes the code about 1.5x faster without any noticeable difference
in the output.
idct: cosmetics: Drop one unnecessary if-block level
xvididct: Ensure that the scantable permutation is always set correctly

This fixes cases where the scantable permuation would get overwritten by
the general idctdsp initialization.
avcodec: Rename xvidmmx IDCT to xvid

The Xvid IDCT is not MMX-specific.
avformat/matroskadec: Check avpriv_new_chapter() for failure

Fixes null pointer dereference

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit '454697603e4efdfc04fadec40518d56c7dc1e5dd'

* commit '454697603e4efdfc04fadec40518d56c7dc1e5dd':
  mpegts: Use av_free() to free memory allocated by av_strdup()

Conflicts:
	libavformat/mpegtsenc.c

See: 92deb28945a5f2b58908d383f183cfc1bc1d7fae
Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit 'e4c9e59a4547adaaa0ce9f25b0d0c5b91ae15472'

* commit 'e4c9e59a4547adaaa0ce9f25b0d0c5b91ae15472':
  mpeg: K&R formatting cosmetics

Conflicts:
	libavformat/mpegenc.c

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit '0026e356d044e72b6e743b234708b8b8af457ac0'

* commit '0026e356d044e72b6e743b234708b8b8af457ac0':
  configure: Die if gas is unavailable under aarch64 as well as ARM

Conflicts:
	configure

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit '444c73583d2848a542330c03949e1f933ac68f53'

* commit '444c73583d2848a542330c03949e1f933ac68f53':
  configure: Only run gas checks on ARM and PowerPC

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit '6f1960ab71b4f18551243ce22d01913108265233'

* commit '6f1960ab71b4f18551243ce22d01913108265233':
  idct: cosmetics: Drop one unnecessary if-block level

Conflicts:
	libavcodec/idctdsp.c

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit '84d173d3de97c753234ab0c0b50551d51413d663'

* commit '84d173d3de97c753234ab0c0b50551d51413d663':
  xvididct: Ensure that the scantable permutation is always set correctly

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Autodetect jpeg-ls files.
avformat/movenc: write reel_name metadata to tmcd atom

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