Adding namespace protection for the ZERO namespace on metawiki.

This grows the placeholder so that new Zero configuration pages
can be created and tested on meta before ZeroRatedMobileAccess's
next version. Once the updated extension is done, this declaration
will be done inside the extension, and removed here.

Change-Id: I6fa447e7b9e2e658c191e2da18d8fd3d3db49e08
Merge "Adding namespace protection for the ZERO namespace on metawiki."