STYLE: more consistency for down-casting

...lugins/blockMeshReader/plugin/pqFoamBlockMeshControls.cxx

...ns/blockMeshReader/plugin/reader/vtkPVblockMeshReader.cxx

src/runTimePostProcessing/fieldVisualisationBase.C

src/runTimePostProcessing/pathline.C

src/runTimePostProcessing/scene.C

src/runTimePostProcessing/volumeFilter.H