CppUnit - C++ port of JUnit Code

tests to include/cppunit/portability/FloatingPoint.h. Changed
implementation assertDoubleEquals to explicitly test for NaN
in case of non-finite values to force equality failure in the
presence of NaN. Previous implementation failed on Microsoft
Visual Studio 6 (on this platform: NaN == NaN).
* examples/cppunittest/TestAssertTest.cpp: Add more unit tests to
test the portable floating-point primitive. Added missing
include <limits>.

* include/cppunit/portability/Makefile.am:
* include/cppunit/portability/FloatingPoint.h: Added file. Extracted
isfinite() from TestAssert.cpp.

* include/cppunit/config-evc4:
* include/cppunit/config-msvc6: Added support for _finite().