Function libcryptsetup_sys::crypt_keyslot_add_by_keyfile

pub unsafe extern "C" fn crypt_keyslot_add_by_keyfile(
    cd: *mut crypt_device, 
    keyslot: c_int, 
    keyfile: *const c_char, 
    keyfile_size: size_t, 
    new_keyfile: *const c_char, 
    new_keyfile_size: size_t
) -> c_int