This reverts commit 6709bdcacd.
There was an issue with the script that removes '-lwebp' from WebP
linker flags, since we're statically linking. This is now fixed.
It's a premultiplied image. This implies that we were misusing encodePNG
in most cases, as we were passing premultiplied pixels which were then
interpreted as unmultiplied. I changed encodePNG to accept premultipled
pixels, and unpremultiply in the implementations.
