Add support for PNG compression in vtkPNGWriter

Change-Id: Ibae911d174ac101f22487459e30d8254a073a0b2
Merge branch 'master' of git://vtk.org/VTK into vtkPNGWriter-compression-support

Change-Id: Icd9f6490f4e74711eae4a1a85dcb014117c70027
Revise comment as per David's suggestion

Change-Id: I8c54b78f6b972cf0504ab2a30efd97275f7c6535
Merge branch 'master' of git://vtk.org/VTK into vtkPNGWriter-compression-support

Change-Id: I810c7209a4279e06d08757d4f3b7e7082e3d314e
Revise comment as per Andrew's suggestion

Change-Id: Ieacca81cf86502b0f618b87ea90f2e730e1b6baa
Merge topic 'vtkPNGWriter-compression-support' into master

f660dc1b Revise comment as per Andrew's suggestion
61ae68a1 Merge branch 'master' of git://vtk.org/VTK into vtkPNGWriter-compression-support
d933d3c8 Revise comment as per David's suggestion
22136194 Merge branch 'master' of git://vtk.org/VTK into vtkPNGWriter-compression-support
5d97d7df Add support for PNG compression in vtkPNGWriter