Partial automation of egg dependencies

[Lassi Kortela]

I have a .egg file for a portable Scheme program substantial enough and 
fast-moving enough that the dependencies are constantly getting out of sync.

Would it be possible to add a feature something like this?

(extension foo.bar
  (source "bar.sld")
  (auto-dependencies)  ; <-- The new feature.
  (csc-options "-R" "r7rs" "-X" "r7rs"))

auto-dependencies would compute the deps by traversing the given source 
file. It would look at csc-options and notice that r7rs is being used. 
Then expect an R7RS-style define-library form in bar.sld, look at 
(import ...) libraries matching those in the .egg and add those to 
component-dependencies, as well as traverse all (include "...") and add 
those to (source-dependencies ...).

If csc-options doesn't say r7rs, it would do the same, but expect 
Chicken module syntax instead.

I wrote some code to grovel r7rs libraries, and there's probably similar 
stuff in csm and Akku.scm too. So if the feature is ok we could stitch 
together the implementation from these.