Fix: invalid array allocation in iss_3d.hpp

If OPENMP is not used, the variable threads_ is zero by default. Thus
the array allocation

   Eigen::Vector3d *omp_mem = new Eigen::Vector3d[threads_];

leads to a valid but zero sized array and finally to an invalid write
at line 381-383 (375-377).
Merge pull request #1022 from jgarstka/iss_3d_bugfix

Fix: invalid array allocation in iss_3d.hpp
Fix: invalid deallocation of arrays used by VTK

Within pcl/visualization, the method SetArray() from the vtkDataArray is
called from several locations in the source code. If not specified, the
vtkDataArray uses free() to deallocate the given memory. But in most
cases (in pcl/visualization) the allocation of arrays is done by new[].
Therefore, VTK_DATA_ARRAY_DELETE was appended as fourth parameter of the
SetArray() method to force the use of delete[] instead.
Merge pull request #1023 from jgarstka/vtk_bugfix

Fix: invalid deallocation of arrays used by VTK