Update ply_io.cpp

Reading a binary PLY file with faces and "vertex_indices" property crashes, if only a PointCloud is provided. Since the polygons_ member is set to 0 and untouched otherwise.

Worked in PCL 1.6, doesn't work right now with 1.7.1.

The ply2pcd sample program provided with PCL crashes as well.
Add libusb-1.0-0-dev for Travis OpenNI support
Improve doxygen doc return
Merge pull request #705 from VictorLamoine/doxygen_improvments

Improve doxygen doc return
Revert "Merge pull request #705 from VictorLamoine/doxygen_improvments"

This reverts commit 5743ecb231d689a883674454d3bf1c1bf8c2bc58, reversing
changes made to 649ed559ac99675902e4bba619bff96395a315dd.
Merge pull request #698 from jspricke/travis_openni2

Add OpenNI2 support to Travis
Improve doxygen doc return
Merge pull request #706 from VictorLamoine/doxygen_improvments

Improve doxygen doc return
Create different variants of the "build" task for gcc and clang

The clang variant remains the same as it was before (i.e. complete
compilation), and the gcc task is reduced to only compiling `pcl_common`
target.
Remove cmake from the install list

This package is guaranteed to be present on Travis
Merge pull request #536 from fran6co/fix-ply

Update ply_io.cpp
Merge pull request #707 from taketwo/simplify-gcc-task-on-travis

Simplify gcc task on Travis
The homebrew formula uses vtk6 now
Merge pull request #713 from fran6co/patch-3

[DOC] The homebrew formula uses vtk6 now