Log Message:
Update to 0.5.1

* Enable various options, Chromium web browser requires them.

Changelog:
- 6/14/2016: version 0.5.1
  This is a binary compatible release.
  * miscellaneous bug fixes (issues #280, #289)
  * reverted alpha plane encoding with color cache for compatibility with
    libwebp 0.4.0->0.4.3 (issues #291, #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 #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