New test for generic Makefile.pre.in
diff --git a/Demo/extend/make_clean b/Demo/extend/make_clean
new file mode 100755
index 0000000..13203cd
--- /dev/null
+++ b/Demo/extend/make_clean
@@ -0,0 +1,5 @@
+#! /bin/sh
+
+# Reset the directory contents.
+
+rm -f Setup* Makefile* *.c *.o *.a *.so *~ python sedscript