dist-hook and rights

[Akim Demaille]

Hi!

When running make distcheck, dist-hook is run twice: once for the
outer tarball, then for the dist performed on the tree built by
distcheck.

There is a big difference between the two though: in the second case,
the tree is read only, which forbids side effects from dist-hook,
which should be valid IMHO.

So maybe we should chmod +w before `make dist' in distcheck?

Thanks!