[Gnu-arch-users] sparse libs and merge fest fun

[Tom Lord]

Got about have of the outstanding merge requests done (mostly by doing
many small ones from Miles).

I've merged in the sparse revision library hack but made a slight 
interface change:

        % tla library-add --sparse REVISION

will add (exactly and only) REVISION to a library but, without
the --sparse flag, library-add works the same as in the past.
(Rather than unconditionally making libraries sparse.)

-t