add log_arrows option to put arrows into the log file

src/API/binary_c_API_debug_fprintf.c

src/API/binary_c_API_log.c

src/API/binary_c_API_make_logstring.c

src/RLOF/RLOF_adaptive_mass_transfer_rate.c

src/RLOF/RLOF_adaptive_mass_transfer_rate2.c

src/RLOF/RLOF_instantaneous_mass_transfer_rate.c

src/binary_c_debug.h

src/binary_c_physical_constants.h

src/binary_c_string_macros.h

src/binary_c_structures.h

src/buffering/binary_c_fail_printf.c

src/common_envelope/common_envelope_evolution_BSE.c

src/debug/debug_colours.h

src/disc/cbdisc_eccentricity_pumping_rate.c

src/disc/disc_F_bisector.c

src/disc/disc_J_bisector.c

src/disc/disc_M_bisector.c

src/disc/disc_bisection_rooter.c

src/disc/disc_build_disc_zones.c

src/disc/disc_calc_disc_structure.c