some cleanups extended the document to cover RelaxNG and tree operations

* relaxng.c: some cleanups
* doc/xmlreader.html: extended the document to cover RelaxNG and
  tree operations
* python/tests/Makefile.am python/tests/reader[46].py: added some
  xmlReader example/regression tests
* result/relaxng/tutor*.err: updated the output of a number of tests
Daniel
diff --git a/python/tests/Makefile.am b/python/tests/Makefile.am
index 761046a..0c16acf 100644
--- a/python/tests/Makefile.am
+++ b/python/tests/Makefile.am
@@ -23,6 +23,9 @@
     reader.py	\
     reader2.py	\
     reader3.py	\
+    reader4.py	\
+    reader5.py	\
+    reader6.py	\
     ctxterror.py\
     readererr.py\
     relaxng.py