Sets or clears keys within the specified key array.
Parameters:
- keys The key array to modify.
- key The keyto add or remove. Key 0 cannot be added or removed, it
is implicitly present in all keyrings. Key 129 cannot be added or removed,
it is implicitly absent from all keyrings (won't even fit, on a normal
system). Specifying an invalid key number causes no error, but no operation
either.
set - If non-zero, the specified key will be added to the keyring. If
zero, the key will be removed.