Add NaNHelper utility

The aim of this helper is to allow to print signaling NaN. This should help to debug uninitialized matrices of vectors values while printing them.

tests/CMakeLists.txt

@@ -85,6 +85,7 @@ add_executable (unit_tests
   test_ListAffectationProcessor.cpp
   test_MathModule.cpp
   test_NameProcessor.cpp
+  test_NaNHelper.cpp
   test_OStreamProcessor.cpp
   test_ParseError.cpp
   test_PETScUtils.cpp