[PATCHES v4] Allow custom testsuite drivers in Automake

[Stefano Lattarini]

OK, in truth these patches are not ready yet, but I'm posting this message
anyway to tell any potential reviewer to ignore older versions of this
series, and concentrate only on the oncoming one, in which I've done (or
plan to do) various fixlets and improvements.  These upcoming patches won't
be perfect either -- but I'd like to stop this continuous respinning, and
any improvoment and polishing can be done in follow-up patches.  So I'd like
to ask to only point out only real errors and bugs, and keep suggestions of
improvoments for follow-up messages (either in this list, or better in CC:
with bug-automake, to have them more visible and persistent).

Thanks, and sorry for the noise,
  Stefano