comptools/autoconf: chmod files to u+w

The autoconf-2.65 tarball contains RO files.
We have to chmod them u+w.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

 reporter_name="Alexander BIGGA"

 reporter_url="http://sourceware.org/ml/crossgcc/2008-07/msg00000.html"

 reporter_comment=""