headers: comment includes in VTKExtensionsDefault

Change-Id: I0a65eeb801ab26b4a77e4e188406c089209a3135
vtkMetaReader: make copy ctor and assignment operator private

Change-Id: Ic0f743efaf5b83a294f7539656f18d0776f23653
Merge topic 'header-fixes' into next

0749dd8f vtkMetaReader: make copy ctor and assignment operator private
d6cf7e68 headers: comment includes in VTKExtensionsDefault