Update webp codec from 0.4.4 to 0.5.1

[WebDev12]

Hi Pierre-Emmanuel, could you please update the webp codec to 0.5.1 when it's released?

The webp codec was updated to 0.5.0 a few months ago with some improvements that you can read about here: https://groups.google.com/a/webmproject ... 5ZF4hgPRkk

Right now, they seem almost ready to release 0.5.1, which is currently at Release Candidate 5. Some highlights: https://groups.google.com/a/webmproject ... dwAxnmzsbw

You can read more about the improvements in 0.5.1, especially for the "near lossless" mode, in Jyrki Alakuijala's comments here: http://encode.ru/threads/2512-Combining ... e-archive)