Makefile.vc: add rudimentary avx2 support

similar to makefile.unix:
> nmake /f Makefile.vc CFG=release-static HAVE_AVX2=1

from the msdn:
The /arch:AVX2 option and __AVX2__ macro were introduced in Visual
Studio 2013 Update 2, version 12.0.34567.1
(Update 2, version 12.0.30501.00 seems to work)

Change-Id: I649ee47c9fdc399fc71a8ac8464728608d9b6412
try to remove the spurious warning for static analysis

Change-Id: Ib81f16c70a0bfad05021401c1cf6788c974b63bd
Merge "Makefile.vc: add rudimentary avx2 support"
lossy decoding: correct alpha-rescaling for YUVA format

The luminance needs to be pre- and post- multiplied by
the alpha value in case of rescaling, for proper averaging.

Also:
- removed util/alpha_processing and moved it to dsp/
- removed WebPInitPremultiply() which was mostly useless
and merged it with the new function WebPInitAlphaProcessing()

Change-Id: If089cefd4ec53f6880a791c476fb1c7f7c5a8e60
(enc|dec)_neon: use vcreate_*() where appropriate

this is more portable than {} initialization.
more involved cases are left for a follow-up.

Change-Id: If8783423d17e90694b168a64ba313ed62ce2cc17
lossless_neon: use vcreate_*() where appropriate

this is more portable than {} initialization.
more involved cases are left for a follow-up.

Change-Id: If7e111864f287ea0a5de6311454aeda37afbb52a
cwebp: add some missing newlines in longhelp output

+ update README

Change-Id: Ia84d8857d575bc29ab3ce9c0f10264c042067e78
cwebp: fallback to native webp decode in WIC builds

this gives precedence to WIC, but attempts to decode the file as WebP if
it fails

Change-Id: I3d894f39a26aea88897a8ebd345139b82f74f312
Always reinit VP8TransformWHT instead of hard-coding

Change-Id: I2012749ed29bd166d2a96555372f0d9baa784385
Merge "(enc|dec)_neon: use vcreate_*() where appropriate"
Merge "lossless_neon: use vcreate_*() where appropriate"
fix missing WebPInitAlphaProcessing call for premultiplied colorspace output

(lossless only)

Change-Id: Ic2d01c8cf9bc1082f07f348733461eb2ee30288a
Merge "cwebp: add some missing newlines in longhelp output"
Merge "cwebp: fallback to native webp decode in WIC builds"
dsp/cpu: NaCl has no support for xgetbv

or the raw opcode; fixes:
  934ed4: unrecognized instruction

Change-Id: I981870baf0e8b03bf40144ea8ec25eff140d5bc3
fix for gcc-4.9 warnings about longjmp + local variables

Needed to add 'volatile' and some casts.
Relevant excerpt from the 'man longjmp':

===============
The values of automatic variables are unspecified after a call to longjmp() if they meet all the following criteria:
  ·  they are local to the function that made the corresponding setjmp(3) call;
  ·  their values are changed between the calls to setjmp(3) and longjmp(); and
  ·  they are not declared as volatile.
===============

Change-Id: Ic72dc92669513a820369ca52a038afa9ec88091f
Optimize VP8SetResidualCoeffs.

Brings down WebP lossy encoding timings by 5%

Change-Id: Ia4a2fab0a887aaaf7841ce6d9ee16270d3e15489
strong filtering speed-up (~2-3% x86, ~1-2% for NEON)

Extract loop invariant and avoid storing/loading samples
if they can be re-used. This is particularly interesting when
a transpose is involved (HFilter16i).

Change-Id: I93274620f6da220a35025ff8708ff0c9ee8c4139
lossy bit-reader clean-up:

* remove LEFT/RIGHT_JUSTIFY distinction. It's all RIGHT_JUSTIFY now.
* simplify VP8GetSigned(), and add some masking branch-less code. Much
  faster on ARM (~13% speed-up). 8% on x86-64, 5% on MacBook.
* split critical implementation into separate bit_reader_inl.h file that
  is only included where needed (vp8.c / tree.c / bit_reader.c)
* bumped BITS value from 16 to 24 for x86-32b too, since it's a bit faster.

Change-Id: If41ca1da3e5c3dadacf2379d1ba419b151e7fce8
remove unused #include's

Change-Id: Icd91a4b6a0bde49145f57e3e74a997822c45792c