Merge pull request #817 from phcerdan/missing_header

COMP: Missing header

Libs/Visualization/VTK/Widgets/ctkVTKDiscretizableColorTransferWidget.cpp

@@ -64,6 +64,7 @@
 #include <vtkImageData.h>
 #include <vtkPiecewiseFunction.h>
 #include <vtkRenderer.h>
+#include <vtkRenderWindowInteractor.h>
 #include <vtkScalarsToColors.h>
 #include <vtkTable.h>