CppUnit - C++ port of JUnit Code

* src/cppunit/XmlOutputter.cpp: extracted class XmlOutputter::Node to
XmlElement. Extracted xml 'prolog' generation to XmlDocument.

* include/cppunit/tools/XmlElement.h:
* src/cppunit/tools/XmlElement.cpp: added, extracted from XmlOutputter::Node.

* include/cppunit/tools/XmlDocument.h:
* src/cppunit/tools/XmlDocument.cpp: added, extracted from XmlOutputter. Handle
XML document prolog (encoding & style-sheet) and manage the root element.

* src/DllPlugInTester/DllPlugInTester.cpp: bug fix, flag --xsl was ignored.

* examples/cppunittest/XmlOutputterTest.h:
* examples/cppunittest/XmlOutputterTest.cpp: updated for XmlOuputter changes.
extracted tests for XmlOutputter::Node to XmlElementTest

* examples/cppunittest/XmlElementTest.h:
* examples/cppunittest/XmlElementTest.cpp: added, tests extracted from
XmlOutputterTest.