comments cleanups use xmllint for doing the RelaxNG tests preparing 2.5.2

* HTMLparser.c tree.c xmlIO.c: comments cleanups
* Makefile.am: use xmllint for doing the RelaxNG tests
* configure.in: preparing 2.5.2 made schemas support default to
  on instead of off
* relaxng.c: removed the verbosity
* xmllint.c: added --relaxng option
* python/generator.py python/libxml_wrap.h: prepared the integration
  of the new RelaxNG module and schemas
* result/relaxng/*: less verbose output
Daniel
diff --git a/python/libxml_wrap.h b/python/libxml_wrap.h
index 56950e9..d1c5dc9 100644
--- a/python/libxml_wrap.h
+++ b/python/libxml_wrap.h
@@ -18,6 +18,7 @@
 #include <libxml/xmlregexp.h>
 #include <libxml/xmlautomata.h>
 #include <libxml/xmlreader.h>
+#include <libxml/relaxng.h>
 
 /**
  * ATTRIBUTE_UNUSED: