dtc expressions

So, in order to actually make progress on the dtc expressions / macros
/ whatnot stuff, I really think I should dust off my integer (constant)
expressions patch, and we can apply that.

While we still have disagreements on a bunch of stuff here, I think
we're at least agreed on what integer expressions should look like.
And even if we change approaches later (e.g. to your ifs and fors in
dtc approach) the integer expression syntax won't change, only the
implementation.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson