changed grsd.hpp and harris_2d.hpp

changed line 90 - sqrt(3) to std::sqrt(3.0) - in grsd.hpp 
and line 340, 376, 412 - size_t to int - in harris_2d.hpp
http://www.pcl-users.org/grsd-hpp-causes-building-errors-Windows-7-x64-msvc2010-td4035138.html