update libwebp from 0.5.0 to 0.6.0

[alexodus]

These are the cumulative changelogs:

• 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 rebuild all libs for android with clang+libc++. #310, fix bug: pops one element from the stack when lua_istable return zero. #314, Curl not getting added for ios project in cocos2dx v3.17  #316, Add mising android.mk for libuv & tvos prebuild libs #322), cwebp/libwebp (issue
    fix box2d warning #312)
  • full libwebp (encoder & decoder) iOS framework; libwebpdecoder
    WebP.framework renamed to WebPDecoder.framework (issue Remove vs2013 #307)
  • CMake support for Android Studio (2.2)
  • miscellaneous build related fixes (issue Update glfw to 3.2.1 #306, cmake properties add folder External #313)
  • miscellaneous documentation improvements (issue fix compiling error using ndk r11+ #225)
  • minor lossy encoder fixes and improvements

• 6/14/2016: version 0.5.1
  This is a binary compatible release.

  • miscellaneous bug fixes (issues [android] Adds tremolo for decoding ogg, pvmp3dec for decoding mp3, these two libraries are from android source code. #280, [tinydir] Compile error fix for win10 #289)
  • reverted alpha plane encoding with color cache for compatibility with
    libwebp 0.4.0->0.4.3 (issues Adds libmd5-rfc library #291, fix warnings #298)
  • lossless encoding performance improvements
  • memory reduction in both lossless encoding and decoding
  • force mux output to be in the extended format (VP8X) when undefined chunks
    are present (issue Fix class_table_get_index #294)
  • gradle, cmake build support
  • workaround for compiler bug causing 64-bit decode failures on android
    devices using clang-3.8 in the r11c NDK
  • various WebPAnimEncoder improvements