Implementation of an OpenMP-parallelized version of Moving Least Squares

As discussed on pcl-devel (http://www.pcl-developers.org/Open-MP-enabled-Moving-Least-Squares-td5707681.html), here's a patch that adds OpenMP parallelization for Moving Least Squares through a class MovingLeastSquaresOMP. Tests are re-enabled and pass without errors. I have been using the patch for quite a while now and it seems stable. I didn't test the upsampling methods thoroughly, though.