http://www.mediawiki.org/wiki/User:Catrope/Stub_threshold shows us people setting...

mediawiki.org/wiki/User:Catrope/Stub_threshold shows us people setting it to insanely large values trying to disable it.
r70433 addressed the UI. Here we proxy its access via a new method getStubThreshold() that disables it if a page of such size cannot be
created (by an user), so we can serve them parser cached articles again.