Function authenticator::rust_u2f_mgr_sign

#[no_mangle]
pub unsafe extern "C" fn rust_u2f_mgr_sign(
    mgr: *mut U2FManager, 
    flags: u64, 
    timeout: u64, 
    callback: extern "C" fn(_: u64, _: *mut U2FResult), 
    challenge_ptr: *const u8, 
    challenge_len: usize, 
    app_ids: *const Vec<AppId>, 
    khs: *const Vec<KeyHandle>
) -> u64