scd: Allow standard keyref scheme for app-openpgp.
* scd/app-openpgp.c (do_change_pin): Allow prefixing the CHVNO with "OPENPGP." * tools/card-call-scd.c (scd_change_pin): Change API to use strings. * tools/gpg-card-tool.c (cmd_passwd): Adjust for change. (cmd_unblock): Ditto.
The generic keyref allows for better error detection in case a keyref
is send to a wrong card.
- Signed-off-by: Werner Koch <email@example.com>