BUG: Memory leak identified by cppcheck

[itkMABMISSimulateData.hxx:207]: (error) Memory leak: coeff
STYLE: Remove useless define

The ITK_EXPORT was always defined as an empty define since
2003, and has no useful meaning.
STYLE: Avoid polluting global namespace

Remove the "using namespace std" so that the global
namespace is not polluted.