Code formatting.

examples/main.c

src/common_io.h

src/engine.c

src/engine.h

src/gravity.c

src/parser.c

src/runner_doiact_grav.h

src/swift_vel_part.h

src/velociraptor_interface.c

src/velociraptor_interface.h

tests/testParser.c

tests/testPotentialPair.c