Update io.hpp

[mhoedlmo]

Updated pcl::CopyPointCloud in oder to be able to compile Kinfu example

[jspricke]

Hi mhoedlmo, can you please add a comment where this is failing? Also, can you fix it according to the style guide [1](there is a space missing in front of the)?

Thanks!

[1] http://www.pointclouds.org/documentation/advanced/pcl_style_guide.php

[messo]

Hi!

I've came across with this issue also, the solution was posted here: http://www.pcl-users.org/failed-to-build-kinfu-td4032311.html (Same as this pull request)
Although I found the same error in correspondance_estimation.hpp of the registration module/project and along the compilation of trunk I've found a couple more. Please find my pull request here: #592

[jspricke]

Fixed with #593.