gpg: Change --print-pka-records into an option.

* g10/gpg.c (aPrintPKARecords): Rename to oPrintPKARecords and do not
use it as a command.
* g10/keylist.c (list_keyblock): List PKA rceords also for secret
keys.

An option allows to use it more flexible. For example to select only
secret keys.

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