Several classes should be PIMPLized
This issue was created automatically from an original Mantis Issue. Further discussion may take place here.
There are several classes in Common and other kits that include implementation specific code in the header file, which forses them to include system files. This polutes namespace of VTK. Example of the kind of classes is vtkMultiThreader. The code should be PIMPLized so that only cxx file needs to include system header files.