bump minimum required autoconf version and revise autogen.sh

test/autogen.sh

@@ -1,12 +1,11 @@
 #!/bin/sh
-#
-# Regenerate configuration files
+
 cp acinclude.m4 aclocal.m4
-found=false
-for autoconf in autoconf autoconf259 autoconf-2.59
-do if which $autoconf >/dev/null 2>&1; then $autoconf && found=true; break; fi
-done
-if test x$found = xfalse; then
-    echo "Couldn't find autoconf, aborting"
-    exit 1
+
+if test "$AUTOCONF"x = x; then
+  AUTOCONF=autoconf
 fi
+
+$AUTOCONF || exit 1
+rm aclocal.m4
+rm -rf autom4te.cache