Log Message:
Update to 0.6.0

Patch from spz@. Thank you.

Changelog:
- 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.

- 12/13/2016: version 0.5.2
  This is a binary compatible release.
  This release covers CVE-2016-8888 and CVE-2016-9085.
  * further security related hardening in the tools; fixes to
    gif2webp/AnimEncoder (issues #310, #314, #316, #322), cwebp/libwebp (issue
    #312)
  * full libwebp (encoder & decoder) iOS framework; libwebpdecoder
    WebP.framework renamed to WebPDecoder.framework (issue #307)
  * CMake support for Android Studio (2.2)
  * miscellaneous build related fixes (issue #306, #313)
  * miscellaneous documentation improvements (issue #225)
  * minor lossy encoder fixes and improvements