Check to only build in_hand_scanner when OpenNI is available
Only build pcd_select_object_plane.cpp when QHull is available

As pcd_select_object_plane.cpp requires QHull it should be excluded when QHull is not found.
Added vtkPolyLine.h header to example_supervoxels.cpp

In 1.7.0 the supervoxel example doesn't build with Visual Studio 2012 (and others: https://github.com/PointCloudLibrary/pcl/issues/202).
Fix a bug in RegionGrowing with oversized output cluster vector.

The clusters vector output by RegionGrowing<PointT, NormalT>::extract()
function was not properly trimmed after filtering out clusters that are
too small and too large. As a result many dozens/hundreds of zero-sized
clusters seeped into the output vector.
Removed compiler options resulting in a D8021 compiler error in Visual Studio 2012
Use __SSE__ instead of HAVE_SSE_EXTENSIONS
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