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.
This adds support for using cached styles that are stale. They're treated like changing styles; when the refreshed style changed compared to the one we've already had, we're swapping out the entire style, which might cause a slight flicker.
