updated the policy on private mail answers more work on Relax-NG

* README: updated the policy on private mail answers
* relaxng.c: more work on Relax-NG
* test/relaxng/* result/relaxng/*: augmented/updated the
  regression tests
Daniel
diff --git a/test/relaxng/tutor5_2.rng b/test/relaxng/tutor5_2.rng
new file mode 100644
index 0000000..9d749dc
--- /dev/null
+++ b/test/relaxng/tutor5_2.rng
@@ -0,0 +1,9 @@
+<element name="point" xmlns="http://relaxng.org/ns/structure/1.0"
+         datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes">
+  <element name="x">
+    <data type="double"/>
+  </element>
+  <element name="y">
+    <data type="double"/>
+  </element>
+</element>