Function secp256k1_ecdh

pub unsafe extern "C" fn secp256k1_ecdh(
    cx: *const Context,
    output: *mut u8,
    pubkey: *const PublicKey,
    seckey: *const u8,
    hashfp: Option<unsafe extern "C" fn(_: *mut u8, _: *const u8, _: *const u8, _: *mut c_void) -> i32>,
    data: *mut c_void,
) -> i32