Refactor of ixml grammar

In an idle moment, I refactored the grammar. Comments gladly received.
Changes: 
* I hid all nonessential terminals. I know above all Tom was asking for 
this.
* I moved the spaces from the rule for ixml into the rule for rule. Tidier 
and more consistent.
* I renamed S to s.
* I simplified 'namestart', since I realised class L covered all the cases.

I think that's all.

See attachment.

Steven