Optimizations to kspace_style MSM, including improving the single-core performance and increasing the parallel scalability. A bug in MSM for mixed periodic and non-periodic boundary conditions was also fixed.

git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@9597 f3b2605a-c512-4ea7-a41b-209d697bcdaa