Dynamic multidimensional arrays

[Trass3r]

> If you want it to by dynamic all the way, you need to put
> the dimensions in the parens like above. Personally, I _never_ put them  
> in the brackets, even when the dynamic array has just one dimension.  
> It's just
> simpler to always put them in the parens and not worry about it.

Maybe we should force the parens approach even for one dimension.
At least dmd should give better diagnostics. It's damn hard to even find  
that syntax in the docs.