Update closure-util
Add error handler

If the server fails to start, display error message and exit.  Typically this is due to the address being in use.
Merge pull request #1507 from tschaub/update-closure-util

Update closure util.
Fix ol.BrowserFeature.HAS_WEBGL test in side-by-side example
Merge pull request #1523 from fredj/side-by-side

Fix ol.BrowserFeature.HAS_WEBGL test in side-by-side example
Merge remote-tracking branch 'openlayers/master' into vector-api