Update vtkImageDataCleanLabels.h

Visual Studio needs an export here to generate the .lib file. No default export supported
Update vtkMyMinimalStandardRandomSequence.h

Use VTK_EXPORT "__declspec(dllexport)", or Visual Studio will try to import here, which leads to a LNK2019 error.
Merge pull request #3 from Rhodanos/master

Visual Studio related fixes