Backport non-gnulib dependent parts of my use-gnulib topic branch

[Gary V. Vaughan]

In the process of moving our version number tracking (and associated
run-time sanity checks) over to git-version-gen, I ended up with a
full-blown 'use-gnulib' topic branch (which I'll post here after the
next release).

That branch as a whole is potentially destabilizing, but I've backported
the non-gnulib depenedent parts back to master in this series, which I
would like to push before rolling the release.  In addition to more
compatibility with gnulib's announce-gen, this series also tidies up
our bootstrap process quite considerably, and fixes the long-standing
leak of developer tool paths into distributed files bug.

Okay to push?

Cheers,
-- 
Gary V. Vaughan (address@hidden)