Merge branch 'master' into task_graph

INSTALL.swift

configure.ac

m4/ax_cc_maxopt.m4

m4/ax_gcc_archflag.m4

m4/ax_pthread.m4

src/Makefile.am

src/barrier.h

src/cell.c

src/common_io.c

src/dump.c

src/dump.h

src/engine.c

src/engine.h

src/hydro/Gizmo/hydro.h

src/hydro/Gizmo/hydro_io.h

src/logger.c

src/logger.h

src/parallel_io.c

src/runner_doiact_vec.c

src/space.c