Improve compression by better entropy analysis.
Improve compression by better entropy analysis.

Change-Id: I6b56ca8d7d9a046a581baa0e85504136685d1161

webmproject/libwebp,PKRoma/libwebp,PKRoma/libwebp,webmproject/libwebp,PKRoma/libwebp,PKRoma/libwebp,webmproject/libwebp,webmproject/libwebp,PKRoma/libwebp,PKRoma/libwebp,webmproject/libwebp