error[E0658]: use of unstable library feature 'wrapping_int_impl' (see issue #32463)

[fabiao]

Context: redox-os
error[E0658]: use of unstable library feature 'wrapping_int_impl' (see issue #32463)
Solution:
add #![feature(wrapping_int_impl)] to the crate attributes to enable to digest/src/lib.rs