Function fiat_crypto::curve25519_64::fiat_25519_sub

pub fn fiat_25519_sub(
    out1: &mut fiat_25519_loose_field_element,
    arg1: &fiat_25519_tight_field_element,
    arg2: &fiat_25519_tight_field_element
)

The function fiat_25519_sub subtracts two field elements.

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