Merge pull request #794 from akohlmey/tersoff-fixes

src/MANYBODY/pair_tersoff.cpp

src/MANYBODY/pair_tersoff_mod.cpp

src/MANYBODY/pair_tersoff_mod_c.cpp

src/MANYBODY/pair_tersoff_zbl.cpp

src/USER-MISC/pair_tersoff_table.cpp

src/USER-OMP/pair_tersoff_zbl_omp.cpp