Merge branch 'izzard-discs': update to 2.1.1

CHANGES

TODO

configure

doc/binary_c-API.lyx

doc/binary_c2.html

doc/binary_c2.lyx

slow

src/API/binary_c_list_args.c

src/RLOF/RLOF_adaptive_mass_transfer_rate.c

src/binary_c.h

src/binary_c_debug.h

src/binary_c_function_macros.h

src/binary_c_parameters.h

src/binary_c_stellar_types.h

src/binary_c_string_macros.h

src/binary_c_structures.h

src/binary_c_types.h

src/binary_c_version.h

src/binary_star_functions/adjust_radius_derivative.c

src/binary_star_functions/mix_stars_BSE.c