stagefile work part 3

the focus of this is to fix the completely broken Require_stagefile mechanism (as you'll understand from the commit message of the second commit (well, fifth with the part#2 stuff bundled)).

this obviously builds upon part #2 (robustification) in MR #117, which is still pending. i'll rebase once it's merged, but there's no reason to not let you see what's up next and no real reason that review cannot commence i guess.

testing a simple build worked fine, but i plan to next go through all of the files and double check the listed dependencies to be certain since up to now they've just been ignored. i'll push a fix if i spot anything.