register xmlSchemaSetValidErrors, patch from Brent Hendricks in the

* python/libxml.c: register xmlSchemaSetValidErrors, patch from
  Brent Hendricks in the mailing-list
* include/libxml/valid.h HTMLparser.c SAX2.c valid.c
  parserInternals.c: fix #156626 and more generally how to find out
  if a validation contect is part of a parsing context or not. This
  can probably be improved to make 100% sure that vctxt->userData
  is the parser context too. It's a bit hairy because we can't
  change the xmlValidCtxt structure without breaking the ABI since
  this change xmlParserCtxt information indexes.
Daniel
diff --git a/parserInternals.c b/parserInternals.c
index 09f8bb8..42db411 100644
--- a/parserInternals.c
+++ b/parserInternals.c
@@ -1630,6 +1630,7 @@
     if (ctxt->keepBlanks == 0)
 	ctxt->sax->ignorableWhitespace = xmlSAX2IgnorableWhitespace;
 
+    ctxt->vctxt.finishDtd = XML_CTXT_FINISH_DTD_0;
     ctxt->vctxt.userData = ctxt;
     ctxt->vctxt.error = xmlParserValidityError;
     ctxt->vctxt.warning = xmlParserValidityWarning;