parallel tests execution in Automake; new integration branch

[Ralf Wildenhues]

Hello everyone,

I've cleaned up the patch set for parallel tests execution in Automake,
and put most of it in a public branch for people to poke with:
  git clone git://git.savannah.gnu.org/automake.git
  git checkout -t origin/ad-parallel-tests

There are a couple of patches that I've not applied to this branch yet,
I will also post them (on automake-patches) for discussion, after those
which I have already applied.

Review, comments, feedback appreciated!

The branch is based upon a slightly older master.  I have created a
public branch "next" to merge the je-silent and the ad-parallel-tests
branch and current master:
  git checkout -t origin/next

Both ad-parallel-tests and next may be rewound if really necessary, but
I hope that it won't be needed.

Thanks,
Ralf