Use `_star2obj()` instead of `_star2mpfr_mpc()`, in `deg2rad()` and `rad2deg()`.
Use `_star2obj()` instead of `_star2mpfr_mpc()`, in `deg2rad()` and `rad2deg()`.

This means no conversion when the given argument is a Math::GMPz or Math::GMPq object.

trizen/Math-AnyNum,trizen/Math-AnyNum