change a small bit in the way valididy error messages get initialized

* parserInternals.c: change a small bit in the way valididy
  error messages get initialized
* python/TODO python/libxml.c python/libxml2-python-api.xml
  python/libxml2class.txt python/libxml_wrap.h python/types.c:
  added some memory debugging to track leaks at the libxml2 level
* python/tests/*.py: changed all tests to check for leaks,
  there is just one left in XPath extension registrations.
daniel
diff --git a/parserInternals.c b/parserInternals.c
index b8bdaa9..91eeae1 100644
--- a/parserInternals.c
+++ b/parserInternals.c
@@ -2257,16 +2257,14 @@
 	sax->ignorableWhitespace = ignorableWhitespace;
 
     ctxt->vctxt.userData = ctxt;
+    ctxt->vctxt.error = xmlParserValidityError;
+    ctxt->vctxt.warning = xmlParserValidityWarning;
     if (ctxt->validate) {
-	ctxt->vctxt.error = xmlParserValidityError;
 	if (xmlGetWarningsDefaultValue == 0)
 	    ctxt->vctxt.warning = NULL;
 	else
 	    ctxt->vctxt.warning = xmlParserValidityWarning;
 	ctxt->vctxt.nodeMax = 0;
-    } else {
-	ctxt->vctxt.error = NULL;
-	ctxt->vctxt.warning = NULL;
     }
     ctxt->replaceEntities = xmlSubstituteEntitiesDefaultValue;
     ctxt->record_info = 0;