Fixed 7 MSVC2008 Compiler Warning (level 3) C4800: 'const int' : forcing value to bool 'true' or 'false' (performance warning)

- added explicit test "(xxx != 0)" to get a "bool" value out of the "int" expression
- see the MSDN recommandation http://msdn.microsoft.com/en-us/library/b6801kcy(v=vs.90).aspx