build: Remove maintainer-mode flag

It's not parsed:
configure: WARNING: unrecognized options: --enable-maintainer-mode

autogen.sh

@@ -10,5 +10,5 @@ autoreconf -vif || exit 1
 popd
 
 if test -z "$NOCONFIGURE"; then
-    $srcdir/configure --enable-maintainer-mode "$@" && echo "Now type \`make' to compile" || exit 1
+    $srcdir/configure "$@" && echo "Now type \`make' to compile" || exit 1
 fi