Merge branch 'master' into testPeriodicBC

doc/Doxyfile.in

src/collectgroup.c

src/runner.c

src/runner_doiact.h

src/runner_doiact_vec.c

src/runner_doiact_vec.h

src/serial_io.c

src/single_io.c

tests/Makefile.am

tests/difffloat.py

tests/test125cells.c

tests/test27cells.c

tests/test27cells.sh.in

tests/test27cellsPerturbed.sh.in

tests/testPair.c

tests/tolerance_125_perturbed.dat

tests/tolerance_27_perturbed.dat

tests/tolerance_27_perturbed_h.dat