Replacing boost::mt19937 with std::mt19937

[kunaltyagi]

Closes #2803

[kunaltyagi]

In sample_consensus, I've modified a protected member. Should I add #if guards as suggested in #2803?

Also, should this be split between non-API/ABI breaking changes and the breaking changes?

Remaining instances:

outofcore/include/pcl/outofcore/impl/octree_disk_container.hpp:76:    template<typename PointT> boost::mt19937
outofcore/include/pcl/outofcore/impl/octree_disk_container.hpp:80:    boost::uuids::basic_random_generator<boost::mt19937> OutofcoreOctreeDiskContainer<PointT>::uuid_gen_ (&rand_gen_);
outofcore/include/pcl/outofcore/impl/octree_disk_container.hpp:302:          boost::variate_generator<boost::mt19937&, boost::bernoulli_distribution<double> > buffcoin (rand_gen_, buffdist);
outofcore/include/pcl/outofcore/impl/octree_disk_container.hpp:322:          boost::variate_generator<boost::mt19937&, boost::bernoulli_distribution<double> > filecoin (rand_gen_, filedist);
outofcore/include/pcl/outofcore/impl/octree_disk_container.hpp:404:          boost::variate_generator<boost::mt19937&, boost::uniform_int<std::uint64_t> > buffdie (rand_gen_, buffdist);
outofcore/include/pcl/outofcore/impl/octree_disk_container.hpp:423:          boost::variate_generator<boost::mt19937&, boost::uniform_int<std::uint64_t> > filedie (rand_gen_, filedist);
outofcore/include/pcl/outofcore/octree_disk_container.h:301:        static boost::mt19937 rand_gen_;
outofcore/include/pcl/outofcore/octree_disk_container.h:302:        static boost::uuids::basic_random_generator<boost::mt19937> uuid_gen_;
recognition/include/pcl/recognition/3rdparty/metslib/simulated-annealing.hh:154:    boost::mt19937 rng;
recognition/include/pcl/recognition/3rdparty/metslib/simulated-annealing.hh:155:    boost::variate_generator< boost::mt19937, boost::uniform_real<double> > gen;
sample_consensus/include/pcl/sample_consensus/sac_model.h:99:        rng_gen_.reset (new boost::variate_generator<boost::mt19937&, boost::uniform_int<> > (rng_alg_, *rng_dist_));
sample_consensus/include/pcl/sample_consensus/sac_model.h:124:        rng_gen_.reset (new boost::variate_generator<boost::mt19937&, boost::uniform_int<> > (rng_alg_, *rng_dist_));
sample_consensus/include/pcl/sample_consensus/sac_model.h:156:        rng_gen_.reset (new boost::variate_generator<boost::mt19937&, boost::uniform_int<> > (rng_alg_, *rng_dist_));
sample_consensus/include/pcl/sample_consensus/sac_model.h:551:      boost::mt19937 rng_alg_;
sample_consensus/include/pcl/sample_consensus/sac_model.h:557:      std::shared_ptr<boost::variate_generator< boost::mt19937&, boost::uniform_int<> > > rng_gen_;

[kunaltyagi]

Closing as per #3996