This reduces the size of the ICU data files from 10.3 MB to 6.6 MB (uncompressed). Also allows us to remove version specific hacks from libTXT and dependencies.
* Remove time
* Remove rand
* Remove array buffers
* Remove more code
* Remove more image decoding code
* Remove more code
* Remove old public API
* Remove more old public headers
* Remove layout test support
* Remove WebPrivateOwnPtr
* Remove WebString
* Remove worker pool