windows: check for _WIN32, not WIN32

Common/Core/vtkConfigure.h.in

Common/Core/vtkWin32Header.h

Common/System/Testing/Cxx/otherTimerLog.cxx

Filters/FlowPaths/vtkParticleTracerBase.cxx

Filters/FlowPaths/vtkTemporalStreamTracer.cxx

Filters/StatisticsGnuR/vtkRInterface.cxx

IO/Image/Testing/Cxx/TestTIFFReaderMultiple.cxx

IO/Import/vtkVRMLImporter_Yacc.h

IO/LSDyna/private/LSDynaFamily.cxx

IO/LSDyna/private/LSDynaFamily.h

IO/LSDyna/vtkLSDynaReader.cxx

IO/MySQL/vtkMySQLQuery.cxx

Interaction/Style/vtkInteractorStyleUnicam.cxx

Rendering/OpenGL/vtkOpenGLExtensionManager.cxx

Testing/GenericBridge/vtkBridgeExport.h

ThirdParty/VPIC/VPICGlobal.cxx

ThirdParty/VPIC/VPICView.cxx

Utilities/DICOMParser/DICOMAppHelper.cxx

Utilities/MetaIO/vtkmetaio/localMetaConfiguration.h

Utilities/ParseOGLExt/ParseOGLExt.cxx