Add support for keyctl_alter()

Add support for keyctl_alter() in the library:

	long keyctl_alter(key_serial_t id,
			  const char *command,
			  const void *data,
			  size_t data_size);

and expose this through the keyctl command:

	keyctl alter <key> <type> <command> [<data>]
	echo <data> | keyctl palter <key> <type> <command>

Signed-off-by: David Howells <dhowells@redhat.com>
13 files changed