Add explicit plural support for limit report messages

Requested by Purodha Blissenbach in
https://translatewiki.net/wiki/Thread:Support/About_MediaWiki:Limitreport-postexpandincludesize-value/ksh
and
https://translatewiki.net/wiki/Thread:Support/About_MediaWiki:Limitreport-templateargumentsize-value/en

Change-Id: I39bea8a45bdd941ebe417b823936aa599185ae03