Require aclocal 1.11.1 or above for autogen.sh

Require aclocal 1.11.1 or above for autogen.sh

1.11.1 is the version in squeeze and lucid, and we know it works. We
also know that 1.10.1 in hardy and lenny doesn't, nor do 1.10 in etch
and 1.9.6 in dapper. We haven't tested any other version.

With older versions python.m4 is buggy, and results in the package being
built not working on python 2.6 (which uses dist-packages rather than
site-packages as a module directory).

The autogen.sh interpreter is changed to bash, as we need to use the [[
builtin to compare versions with "<". [ doesn't have that functionality,
and we can't of course rely on dpkg, which won't be installed on all
distributions.

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