Fix a regression in streaming entities support

* parser.c: fix a regression in entity parsing when using the reader
  introduced because we were not reusing _private on entities parsing
  context
diff --git a/parser.c b/parser.c
index 4ee9b43..a476060 100644
--- a/parser.c
+++ b/parser.c
@@ -13125,8 +13125,9 @@
 	return(NULL);
     }
 
-	if (pctx != NULL) {
-		ctxt->options = pctx->options;
+    if (pctx != NULL) {
+        ctxt->options = pctx->options;
+        ctxt->_private = pctx->_private;
     }
 
     uri = xmlBuildURI(URL, base);