Merge branch 'parallel_rebuild2' into 'master'

src/cell.c

src/cell.h

src/engine.c

src/engine_maketasks.c

src/lock.h

src/proxy.c

src/runner.c

src/runner_doiact_stars.h

src/timers.h

src/tools.c

src/tools.h

tests/testInteractions.c

tests/testPeriodicBC.c