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.
Remove unnecessary typecasts

goog.asserts.assertInstanceof is sufficient for the compiler to deduce
the type.
Use @inheritDoc in ol.render.webgl.Immediate
Use a switch statement, rather than ifs, in ol.render.canvas.Replay
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 pull request #1522 from twpayne/vector-api-clean-ups

[vector-api] Miscellaneous clean-ups
Merge remote-tracking branch 'openlayers/master' into vector-api
Add ol.geom.Circle
Add ol.render.IRender#drawCircleGeometry
Add ol.render.webgl.Immediate#drawCircleGeometry
Add ol.render.canvas.Immediate#drawCircleGeometry
Add ol.replay.canvas.Instruction.CIRCLE
Add ol.render.canvas.PolygonReplay#drawCircleGeometry
add ol.render.vector.renderCircleGeometry_
Add an ol.geom.Circle to geojson example
Add FIXME to geolocation example
Encode ol.geom.Circles as empty geometry collections in GeoJSON

GeoJSON does not support circles, nor null geometries.  Empty geometry
collections seem to be the way to represent at null geometry in GeoJSON.