configure.ac: add AM_PROG_AR for automake >= 1.12

fixes:
automake-1.12/am/ltlibrary.am: warning: 'libwebp.la': linking libtool libraries using a non-POSIX
automake-1.12/am/ltlibrary.am: archiver requires 'AM_PROG_AR' in 'configure.ac'

Change-Id: I223f93e5f075aaf23cfefceef55e2ab8eeb34ccd
(cherry picked from commit ed4dc717696ddc791363f2301fb4a142d4ef4633)
add WebPBlendAlpha() function to blend colors against background

new option: -blend_alpha 0xrrggbb
also: don't force picture.use_argb value for lossless. Instead,
delay the YUVA<->ARGB conversion till WebPEncode() is called.
This make the blending more accurate when source is ARGB
and lossy compression is used (YUVA).
This has an effect on cropping/rescaling. E.g. for PNG, these
are now done in ARGB colorspace instead of YUV when lossy compression
is used.

Change-Id: I18571f1b1179881737a8dbd23ad0aa8cddae3c6b
(cherry picked from commit e7d9548c9bc94a7c8f2ce70ec81464abb4abf9d6)
pngdec: Avoid a double-free.

Earlier, at line#275, if ok == 0, it would have triggered a double free
of 'rgb'.

Change-Id: Iaee1f35824a66f6e4b488e523416f73b87c5ec30
(cherry picked from commit b68912af2c8cefa52bb16634b077938ff074f03a)
WebPEncode: An additional check.
Start VP8EncLoop/VP8EncTokenLoop only if VP8EncStartAlpha succeeded.

Change-Id: Id1faca3e6def88102329ae2b4974bd4d6d4c4a7a
(cherry picked from commit 67708d67013776fb0aa6593a49249a1b350fe602)
update gitignore

*.a, new examples and new automake-1.12 file (ar-lib)

Change-Id: I28d7bc59a2977a7c5959940936e3d13a71dd149c
(cherry picked from commit 3a15125d2f1916cd42c2f438e6f60d876b63235b)
Makefile.vc: drop /FD flag

breaks under wine; from MSDN:
/FD is only used by the development environment, and it should not be
used from the command line or a build script.

Change-Id: I180c9813e721b163cc645b9b7f14fe36556019d3
(cherry picked from commit c61baf0c10d566ebe92b9a9402f978f950ab9b89)
Makefile.vc: flags cleanup

- drop some unnecessary link flags
- use lib.exe directly for creating libraries
- factorize /nologo and use it consistently

Change-Id: Ie76119bc051e9bc53e4d6bba1a0a3f124f9062fc
(cherry picked from commit 52967498b3ef7fb8c0bdc5cb5934e46edaa069f2)
Makefile.vc: have 'all' target build everything

default is still the core examples as makefile.unix

Change-Id: Ica3fe6123f4359aefa130b39d2b0739b65e34c0b
(cherry picked from commit 69d0f92658ae20017bf23240eaa06523a5f189bb)
Add incremental support for extended format files

This applies to images with optional chunks (e.g. images with ALPH
chunk,
ICCP chunk etc). Before this, the incremental decoding used to work like
non-incremental decoding for such files, that is, no rows were decoded
until
all data was available.

The change is in 2 parts:
- During optional chunk parsing, don't wait for the full VP8/VP8L chunk.
- Remap 'alpha_data' pointer whenever a new buffer is allocated/used in
WebPIAppend() and WebPIUpdate().

Change-Id: I6cfd6ca1f334b9c6610fcbf662cd85fa494f2a91
(cherry picked from commit ead4d478595d0c7b112e42f6766d00b16a39e294)
add precision about dynamic output reallocation with IDecoder

The output surface CAN be changed inbetween calls to
WebPIUpdate() or WebPIAppend(), but with precautions.

Change-Id: I899afbd95738a6a8e0e7000f8daef3e74c99ddd8
(cherry picked from commit ff885bfe1f6e419bec762b28879f7039318eaf4e)
prevent signed int overflow in left shift ops

force unsigned when shifting by 24.

Change-Id: Ie229d252e2e4078107cd705b09397e686a321ffd
(cherry picked from commit f4f90880a8de432cdead8baed1e2b04e1afb6128)
don't forward declare enums

doing so is not part of ISO C; removes some pedantic warnings

Change-Id: I739ad8c5cacc133e2546e9f45c0db9d92fb93d7e
(cherry picked from commit 96e948d7b034d916e959b68e7151405f8a309eaa)
Demux: Fix a potential memleak

Change-Id: Ic0dcac010da088b791c130be4abacdd8c31e92cf
(cherry picked from commit 94328d6457e427da1e0dcf11210f9936fe5c4aeb)
Add missing name to AUTHORS

Change-Id: I00092e5bb676b48abc05b94080b589b48c911c82
(cherry picked from commit 46089b207daf3d0bf30ffa7f04dc7b67edade87f)
gif2webp: Fix ICC and XMP support

Change-Id: Ib5aafef388bd191610e4cc2f8180f35cd454f1d3
(cherry picked from commit b26e5ad540bea568d9c5d7126918465bea200c70)
Remove the gcc compilation comments

They went out of sync some time ago, and are
no longer really required since we have them
buildable from makefile.unix

Change-Id: Ica2dcf5c55f44365598f832f55204d123d7aa601
(cherry picked from commit a4e1cdbbe80af7e4a95ccb5131df6e71d138753b)
configure.ac: add some helper macros

library check related variable maintenance -> *_INCLUDES / *_LIBS

CLEAR_LIBVARS / LIBCHECK_PROLOGUE / LIBCHECK_EPILOGUE

Change-Id: I72e292dc1f69b02f69a26639308f247db0471e2b
(cherry picked from commit 4ef144779260bdd4f4b06d2ccf67f6756e1f0f57)
configure: add --enable-everything

Change-Id: Ie1b3abd42459de7f789fe985759c465c2a196727
(cherry picked from commit 3cafcc9a8de7419d98a3deb456b3c807748eeda7)
Alpha decoding: significantly reduce memory usage

Simply get rid of an intermediate buffer of size width x height, by
using the fact that stride == width in this case.

Change-Id: I92376a2561a3beb6e723e8bcf7340c7f348e02c2
(cherry picked from commit edccd194362f86ed3b8106dd2474688e4a2a305e)
configure: add GLUT detection; build vwebp

Change-Id: I7f0964db2d04c22ff9ec274e8cd1cbed7379a165
(cherry picked from commit 0e513f7ae3e41c69baba66d1b68749860879a3f6)