libwebp-0.6.0

- 1/26/2017: version 0.6.0
  * lossless performance and compression improvements
  * miscellaneous performance improvements (SSE2, NEON, MSA)
  * webpmux gained a -duration option allowing for frame timing modification
  * new img2webp utility allowing a sequence of images to be converted to
    animated webp
  * API changes:
    - libwebp:
      WebPPictureSharpARGBToYUVA
      WebPPlaneDistortion
    - libwebpmux / gif2webp:
      WebPAnimEncoderOptions: kmax <= 0 now disables keyframes, kmax == 1
                              forces all keyframes. See mux.h and the gif2webp
                              manpage for details.

update ChangeLog

Change-Id: Ibaa88480519114b8f36f96c51d44b5c3b8a6433d

• ChangeLog[diff]