CppUnit - C++ port of JUnit Code

* include/cppunit/extensions/TestFixtureFactory.h: extracted from
HelperMacros.h. Added template class ConcretTestFixtureFactory.

* include/cppunit/extensions/TestSuiteBuilderContext.h:
* src/cppunit/TestSuiteBuilderContext.cpp: added. Context used
to add test case to the fixture suite. Prevent future
compatibility break for custom test API.

* include/cppunit/extensions/HelperMacros.h: mostly rewritten. No
longer use TestSuiteBuilder. Added support for abstract test fixture
through macro CPPUNIT_TEST_SUITE_END_ABSTRACT. Made custom test API
easier to use.

* examples/cppunittest/HelperMacrosTest.h:
* examples/cppunittest/HelperMacrosTest.cpp: updated against
HelperMacros.h changes.