also fix CElement::removeAttributeNode* to save the prefix.

 CAttr::getSpecified() should return true.
 CAttr::getValue() and CElement::setAttributeNode() could crash if no children.
 CAttributesMap::*NS() methods ignored namespaceURI parameter.
 CDATASection::getNodeValue() forwarded to wrong base class.
 CDocument needs to override cloneNode().
 CDocument::importNode(), CDocumentBuilder::parseURI() deref null argument.
 CElement::getAttributes() should return an empty map.
 CElementList could be created for null element.
 CNode::insertBefore() did not set parent/children pointers.
 CNode::setPrefix() should only work on element/attribute.
 CXPathAPI had inverted check for null argument (xmlfix3 regression).

 new method CNode::IsChildTypeAllowed(NodeType).
 use it in appendChild(), insertBefore(), replaceChild().

 add namespace data member to CAttr.
 CAttr overrides getPrefix(), setPrefix(), getNamespaceURI().
 CDocument::createAttributeNS() uses this new CAttr member instead of creating
  a dummy carrier element.
 CElement::setAttributeNode_Impl_Lock() and CNode::appendChild() do not free
  the no longer existing dummy carrier element.
 CNode::insertBefore() calls appendChild() for attributes
  instead of ignoring namespace.
 CNode::appendChild() does not invalidate attributes, because they are copied.

 add some additional argument checks.
 return value of xmlGetProp was leaked.
 invalidate CAttr instances after calling xmlUnsetProp.

 add some additional argument checks.
 fix mess in CNode::setPrefix().

 also initialize member variables in constructors.

 use CDocument mutex in results, and during evaluation.
 new CXPathAPI member mutex.
 also, fix lcl_collectNamespaces in case parent nodes declare same prefix.

 use it to lock all CNode and derived classes' UNO methods.

 instead now the CDocument contains a node map member.

 (and in the next patch, an actual CDocument, not just 0 :)

 replace Reference<XNode> with Reference<CDocument>.
 also remove all using namespace css::lang, due to conflicts.

 member pointer does not keep document alive.
 also, if an attribute is unlinked, it is leaked.

 the string buffer allocated in ctor missed null terminator.
 the xmlChar* members of ElementList are leaked.
 the CElement* pointer does not keep the document alive.
 CDocument::getElementsByTagNameNS calls CElementList ctor with wrong args.

 capture listener was not called for first node in vector.
 (assuming that it was intended to be called)

 instead CDocument now has a CEventDispatcher member.