C library headers

[Benjamin Kosnik]

> I'm sorry, Anthony, I misunderstood what you were doing.  Most of the 
> work for "shadow" headers has already been done, and is in the tree
> under /shadow, along with scripts mkshadow and inclosure.  It just 
> needs to be finished, including ...
> > POSIX and XOPEN stuff (it'll just take a little
> > longer :(

note:

we should probably make inclosure -> mkinclosure, since all the rest of
the scripts start with mk, and it seems like a good convention to have.

-benjamin