create a tag with attributes, namespace and adds 'xmlns' if needed.
Parameter
string $qname - qualified tag name
array $attributes - assoc array with attributes
string $content - string content of the tag
string $namespaceUri - URI of the namespace if xmlns attribute should be added
integer $replaceEntities - whether to replace XML entities in content, embedd it in a CData section or leave it untouched.
Possible values are FALSE, XML_UTIL_REPLACE_ENTITIES or XML_UTIL_CDATA_SECTION.
