Make fixes for VTK 6

This fixes compilation errors encountered when building PCL
against VTK 6 (from the current git master). The changes are
based on the recommendations in the VTK 6 migration guide [1].

This closes issue #199.

[1] http://www.vtk.org/Wiki/VTK/VTK_6_Migration_Guide
Make fixes for VTK 6

This fixes compilation errors encountered when building PCL
against VTK 6 (from the current git master). The changes are
based on the recommendations in the VTK 6 migration guide [1].

This closes issue #199.

[1] http://www.vtk.org/Wiki/VTK/VTK_6_Migration_Guide
More VTK 6 fixes
Updates for VTK6 - avoiding Image_viewer_

LG