yui-compressor can't compress jQuery 2.2+

[cburschka]

As seen in yui/yuicompressor/issues/234, jQuery 2.2+ uses ES5 syntax that yui-compressor does not accept.

This means JS compression is broken for now, until we find a new compressor.

A short term solution might be to exclude jQuery from JS aggregation and just use jquery.min.js as distributed from the CDN (or for that matter return to linking to the CDN directly, because adding it to the source tree wasn't that great in hindsight). However, as libraries (and core code) are increasingly adopting ES5 syntax, this will not help in the long run.