fix autotools support

autogen.sh

 #!/bin/sh
+mkdir -p config
 autoreconf --force --install -I config -I m4

configure.ac

 AC_INIT(nomad, 3.6.1, miroslav.shaltev@shaltev.de)
-AC_PREREQ([2.69])
+AC_PREREQ([2.67])
 AC_CONFIG_HEADERS([config.h])
 
 # Checks for programs.