Merge pull request #570 from akohlmey/collected-small-changes

doc/src/fix_rigid.txt

examples/README

src/KSPACE/pppm.cpp

src/KSPACE/pppm_disp.cpp

src/RIGID/fix_rigid.cpp

src/RIGID/fix_rigid_small.cpp

src/USER-OMP/fix_nphug_omp.cpp

src/USER-OMP/fix_qeq_comb_omp.cpp

src/USER-REAXC/reaxc_allocate.cpp

src/comm_brick.cpp

src/fix_enforce2d.cpp