BUG: special: fix up corner case accuracy in binom()
TST: special/_testutils: deal with ignore_inf_sign properly
BUG: special: fix intermediate overflow + handle negative integer cases in beta()
BUG: special: deal with loss of precision in binom(n, k) for |k| >> |n|
TST: special/mpmath: always test at least one negative integer and half-integer
TST: special/mpmath: use a finite atol in besseli tests + mark half-integer bessel y issue