EBNF wiki markup

MediaWiki should have an EBNF wiki markup, known as Extended Backus-Naur form which is a formalized way to represent grammar. Bug 7 corresponds to this page. There's not much stuff here though.

Links to EBNF stuff

 * http://www.cl.cam.ac.uk/~mgk25/iso-ebnf.html
 * http://www.garshol.priv.no/download/text/bnf.html