Merge tag 'v1.0.0'

libwebp-1.0.0

- 4/2/2018: version 1.0.0
  This is a binary compatible release.
  * lossy encoder improvements to avoid chroma shifts in various circumstances
    (issues #308, #340)
  * big-endian fixes for decode, RGBA import and WebPPictureDistortion
  Tool updates:
    gifwebp, anim_diff - default duration behavior (<= 10ms) changed to match
                         web browsers, transcoding tools (issue #379)
    img2webp, webpmux - allow options to be passed in via a file (issue #355)

* tag 'v1.0.0': (23 commits)
  update ChangeLog
  webp-container-spec: correct frame duration=0 note
  vwebp: Copy Chrome's behavior w/frame duration == 0
  update ChangeLog
  add WEBP_DSP_INIT / WEBP_DSP_INIT_FUNC
  fix 16b overflow in SSE2
  makefile.unix: add DEBUG flag for compiling w/ debug-symbol
  cwebp,get_disto: fix bpp output
  cmake: Make sure we use near-lossless by default.
  fix bug in WebPImport565: alpha value was not set
  update ChangeLog
  Revert "Use proper targets for CMake."
  Use proper targets for CMake.
  Remove some very hard TODOs.
  {de,}mux/Makefile.am: add missing headers
  makefile.unix,dist: use ascii for text output
  add -version option to anim_dump,anim_diff and img2webp
  webp_js: fix webp_js demo html
  update ChangeLog
  update AUTHORS
  ...

Change-Id: I5659406c022a0964f728ce2eb35338fd9c195466