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An incorrect libraries/ prefix was being added.

The packages file has an extra component (for "darcs" or "git") so we need
to take that into account when grepping.

find on Windows doesn't understand -L, so stop trying to be clever and
just autoreconf everything.

Also, print out the names of directories as we autoreconf them, so that
if autoreconfing one breaks then we know which one it was.

Two problems here: find needs to dereference symbolic links (-L
option, I really hope that's portable), and we need to notice when
aclocal.m4 is updated.  

Somehow I think this was easier when it just always ran
autoreconf... what was wrong with that?

* Call autoreconf only if necessary, avoiding a strict tool dependency.
* Be a good *nix citizen and don't clutter the output when everything is fine.
* Make a few more scripts executable.

gmp is now in a top-level directory and we only have the tarball in the
darcs repo. It gets untarred if it is needed.

This fixes a problem where patches altering the darcs-all script break
on Windows as the file is open. The script is now also slightly nicer,
on balance.

It used to be the case that
    autoreconf
in the root would also autoreconf in any libraries that need it, and
    ./configure
in the root would also configure all the libraries.

However, cabal now configures the libraries, so they were getting
configured twice.

Thus now a small shellscript, boot, autoreconfs the root and all libraries
that need it, and ./configure in the root doesn't configure the libraries.