`modular`: Reduce larger bit-sizes to smaller ones.

[github-actions[bot]]

On 2022-06-03 @recmo wrote in 2f6a5d6 “Merge pull request #103 from recmo/mulmod”:

Reduce larger bit-sizes to smaller ones.

    /// ⚠️ Compute $\mod{\mathtt{self}}_{\mathtt{modulus}}$.
    ///
    /// **Warning.** This function is not part of the stable API.
    ///
    /// Returns zero if the modulus is zero.
    // FEATURE: Reduce larger bit-sizes to smaller ones.
    #[must_use]
    pub fn reduce_mod(mut self, modulus: Self) -> Self {
        if modulus == Self::ZERO {
            return Self::ZERO;
        }

From src/modular.rs:14