fixed a "registering on an undefined event" warning when `visibilityChange` is not supported (i.e. CocoonJS)

I'm not sure if the event is actually supported or not by cocoonJS, as
feedback from the following ticket seems to suggest the opposite :
https://github.com/melonjs/melonJS/issues/432
Merge remote-tracking branch 'upstream/master'
Merge branch 'master' into 1.1.0-dev