gpg: Add a notation to encryption subkeys in de-vs mode.
* g10/keygen.c (struct opaque_data_usage_and_pk): Add cpl_notation. (do_add_notation): New. (keygen_add_key_flags_and_expire): Set cpl@gnupg.org notation if requested. (write_keybinding): Request notation for subkeys in de-vs mode.
- GnuPG-bug-id: T6279