Nowadays we have actual files (tracket by VCS) in autotools/, so we know
the directory exists.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>

Reviewed-by: iustinp

Not all distributions have the same version of aclocal, autoconf
or automake. Users can pass the name of a specific executables
via environment variables. Change configure.ac to require at
least autoconf 1.9.

Reviewed-by: iustinp

This patch adds checking for our external python modules at the
./configure stage, as it's better to check than rely on documentation.

The patch adds one autoconf macro from the autoconf macro archive
(http://autoconf-archive.cryp.to)

Reviewed-by: imsnah

Reviewed-by: ultrotter