fix off-by-one bug in buffer re-allocator

src/MANYBODY/pair_sw.cpp

src/MANYBODY/pair_tersoff.cpp

src/MANYBODY/pair_vashishta.cpp

src/MANYBODY/pair_vashishta_table.cpp

src/USER-OMP/pair_sw_omp.cpp

src/USER-OMP/pair_tersoff_omp.cpp

src/USER-OMP/pair_vashishta_omp.cpp

src/USER-OMP/pair_vashishta_table_omp.cpp