fix for ImageViewer using VTK 5.10.1
Merge pull request #63 from aichim/master

Fix for VTK 5.10.1
* fixed issue #992 (http://dev.pointclouds.org/issues/992). Thanks Jan!
* implemented feature #993 (http://dev.pointclouds.org/issues/993). Thanks Jan!
Fix issue #994 thanks to Jan Oberländer
Merge pull request #69 from nizar-sallem/fix_on_left_button_up

Fix issue #994 thanks to Jan Oberländer
fix for ImageViewer using VTK 5.10.1
* fixed issue #992 (http://dev.pointclouds.org/issues/992). Thanks Jan!
* implemented feature #993 (http://dev.pointclouds.org/issues/993). Thanks Jan!
Fixing issue #994 thanks to Jan Oberländer
Merge branch 'master' of github.com:PointCloudLibrary/pcl into bugfix988