fixes a libtool problem on AMD 64bits builds found the validation problem

* libxml.spec.in: fixes a libtool problem on AMD 64bits builds
* relaxng.c: found the validation problem I had with interleave
  when not covering all remaining siblings
* Makefile.am test.relaxng/* result/relaxng/*: augmented the
  testsuite and check the RNG schemas against the RNG schemas
  given in appendix A
Daniel
diff --git a/result/relaxng/tutor11_2_valid b/result/relaxng/tutor11_2_valid
new file mode 100644
index 0000000..3294c13
--- /dev/null
+++ b/result/relaxng/tutor11_2_valid
@@ -0,0 +1 @@
+./test/relaxng/tutor11_2.rng validates