[XMLSCHEMA-39] Create a proper xmlns namespace qualified attribute

diff --git a/xmlschema-core/src/main/java/org/apache/ws/commons/schema/SchemaBuilder.java b/xmlschema-core/src/main/java/org/apache/ws/commons/schema/SchemaBuilder.java
index ed910c8..ca56f26 100644
--- a/xmlschema-core/src/main/java/org/apache/ws/commons/schema/SchemaBuilder.java
+++ b/xmlschema-core/src/main/java/org/apache/ws/commons/schema/SchemaBuilder.java
@@ -1005,7 +1005,8 @@
                     }

                     String namespace = ctx.getNamespaceURI(prefix);

                     if (!Constants.NULL_NS_URI.equals(namespace)) {

-                        Attr nsAttr = attrEl.getOwnerDocument().createAttribute("xmlns:" + prefix);

+                        Attr nsAttr = attrEl.getOwnerDocument().createAttributeNS(Constants.XMLNS_ATTRIBUTE_NS_URI,

+                                                                                  "xmlns:" + prefix);

                         nsAttr.setValue(namespace);

                         attrs.add(nsAttr);

                     }