gpg: Introduce magic value 25519 to switch a card to ECC.
* g10/card-util.c (show_keysize_warning): Slightly change the text. (ask_card_keyattr): Handle special value 25519. (do_change_keyattr): Allow changing to cv25519/ed25519. (generate_card_keys): Ditto. (card_generate_subkey): Ditto.
This is kludge to make it easier for gnuk to be switched into ECC
mode.
- Signed-off-by: Werner Koch <wk@gnupg.org>