moving binary_log_loss out of src/stan/math/special_functions.hpp
moving softmax out of src/stan/math/special_functions.hpp
moving inverse_softmax out of src/stan/math/special_functions.hpp
moving log1p out of src/stan/math/special_functions.hpp
moving log1p out of src/stan/math/special_functions.hpp
moving log1m out of src/stan/math/special_functions.hpp