[0/4] Input file and srcpos rework (resend)

[David Gibson]

More clearing of my backlog of dtc patches.  This is a rebased series
of patches I sent out several months back to clean up the handling of
source files and positions.  This is a bit less trivial than the other
patches I've been resending recently, though it's far from rocket
science.

-- 
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