Function fiat_crypto::poly1305_64::fiat_poly1305_sub

pub fn fiat_poly1305_sub(
    out1: &mut fiat_poly1305_loose_field_element,
    arg1: &fiat_poly1305_tight_field_element,
    arg2: &fiat_poly1305_tight_field_element
)

The function fiat_poly1305_sub subtracts two field elements.

Postconditions: eval out1 mod m = (eval arg1 - eval arg2) mod m