test failures with Rust 1.84 and newer

[decathorpe]

---- ascii_char::tests::is_digit_strange_radixes stdout ----
thread 'ascii_char::tests::is_digit_strange_radixes' panicked at (...)/rustc-1.84.0-src/library/core/src/char/methods.rs:391:9:
to_digit: invalid radix -- radix must be in the range 2 to 36 inclusive
failures:
    ascii_char::tests::is_digit_strange_radixes

This seems to be caused by a behaviour change in the Rust standard library as of version 1.84.0 (Pull Request, commit).

Would it make sense to follow the standard library here, and forbid invalid radixes 0 and 1?