Fixed various clang -Wmissing-variable-declarations warnings

Common/Core/Testing/Cxx/TestLoggerThreadName.cxx

Common/Core/vtkLogger.cxx

Common/Core/vtkOutputWindow.cxx

...taModel/Testing/Cxx/TestHyperTreeGridGeometricLocator.cxx

...tionModel/Testing/Cxx/TestAbortExecuteFromOtherThread.cxx

Common/System/vtkTimerLog.cxx

Filters/AMR/Testing/Cxx/TestAMRAbortExecute.cxx

Filters/Core/vtkArrayCalculator.cxx

IO/Cesium3DTiles/Testing/Cxx/TestCesium3DTilesWriter.cxx

Rendering/OpenGL2/Testing/Cxx/TestPropPicker2Renderers.cxx

Rendering/OpenGL2/vtkOpenGLRenderWindow.cxx