Bug#169207: needs to build depend on autoconf2.13
Justification: arm autobuilder can't cope otherwise
Autoconf 2.50 doesn't seem to work for building gcc 3.1 (it triggers the
"recursion limit reached" problem). For gcc-3.0, changing the build
dependency from autoconf to autoconf2.13 fixed this, and I guess the
same would work for gcc-3.1.
I would have uploaded a new package with this change, but I was stymied
by libstdc++ compilation problems (see separate report).