configure: Fix aclocal include dir

This readds -I m4 to the aclocal parameters that was dropped by the
previous commit.

The problem is that AC_CONFIG_MACRO_DIR() macro in autoconf was broken
until recently, see:

http://lists.gnu.org/archive/html/autoconf/2013-08/msg00013.html

Reported-by: Vinson Lee <vlee@twopensource.com>
Reported-by: Joseph Beckenbach <jbeckenbach@lancope.com>
Signed-off-by: Cyril Hrubis <chrubis@suse.cz>