Merge branch 'master' into 'updated_MAC'

src/cooling/const_du/cooling.h

src/cooling/const_du/cooling_io.h

src/cooling/const_lambda/cooling.h

src/cooling/const_lambda/cooling_io.h

src/cooling/none/cooling_io.h

src/distributed_io.c

src/engine.c

src/engine.h

src/hydro/AnarchyPU/hydro.h

src/hydro/Default/hydro.h

src/hydro/Gadget2/hydro.h

src/hydro/Minimal/hydro.h

src/hydro/PressureEnergy/hydro.h

src/hydro/PressureEnergyMorrisMonaghanAV/hydro.h

src/hydro/PressureEntropy/hydro.h

src/hydro/SPHENIX/hydro.h

src/hydro/SPHENIX/hydro_parameters.h

src/line_of_sight.c

src/line_of_sight.h

src/parallel_io.c