Xerces 2.12.0: DOM Implementation

This update focuses on the xerces/dom package. Starting with the following bugs fixed in 2.12.0:

XERCESJ-1667 -- ClassLoader memory leak via stacktrace in pre-created DOMNormalizer.abort exception
XERCESJ-1522 - Trailing spaces in DOMMessages.properties
XERCESJ-1501 - Namespace declarations not always pruned from the DOM when the "namespace-declarations" parameter is set to false.
XERCESJ-1582 - Node prefix/namespace query methods throw an NPE on a document without a document element
XERCESJ-1421 - Temporary inconsistent data inside Xerces2-J when removing a first child of a node.


Updates the following classes:
xerces/internal/dom/AttrImpl.java
xerces/internal/dom/AttrNSImpl.java
xerces/internal/dom/ChildNode.java
xerces/internal/dom/CoreDOMImplementationImpl.java
xerces/internal/dom/DOMConfigurationImpl.java
xerces/internal/dom/DOMNormalizer.java
xerces/internal/dom/DeferredDocumentImpl.java
xerces/internal/dom/DocumentTypeImpl.java
xerces/internal/dom/ElementImpl.java
xerces/internal/dom/ElementNSImpl.java
xerces/internal/dom/NamedNodeMapImpl.java
xerces/internal/dom/NodeImpl.java
xerces/internal/dom/PSVIDOMImplementationImpl.java
xerces/internal/dom/ParentNode.java
xerces/internal/dom/TextImpl.java

The update covers bug fixes in 2.12.0 and previous versions as listed below, as well as minor changes without bug ids.
XERCESJ-1394 Node.lookupNamespaceURI() sometimes returns an empty string instead of null.
XERCESJ-1248 Static textNode on AttrImpl breaks thread-safety, mutations of independant documents from within a mutation listener, and introduces potential memory leaks
XERCESJ-1125 Small enhancements and tweaks for the org.apache.xerces.dom package
XERCESJ-1133 Need increase in visibility for HTMLElementImpl constructor