scd: Add special serialno compare for OpenPGP cards.

* scd/app.c (is_same_serialno): New.
(check_application_conflict): Use this.
(select_application): Ditto.
(app_switch_current_card): Ditto.
* scd/app-openpgp.c (check_keyidstr): Ignore the card version and also
compare case insensitive.

This is required because we change what we emit as serialno of OpenPGP
cards but existing keys still use the old form of the serial
number (i.e. with a firmware version).

See-commit: 3a8250c02031080c6c8eebd5dea03f5f87f9ddd7

• Signed-off-by: Werner Koch <wk@gnupg.org>