gpg: New option --quick-update-pref.
* g10/gpg.c (aQuickUpdatePref): New. (opts): Add --quick-update-pref. (main): Implement. * g10/keyedit.c (keyedit_quick_update_pref): New. (menu_set_preferences): Add arg 'unattended' and adjust caller.
This new quick command is in particular useful to update existing keys
so that they can be used with OCB mode.
(cherry picked from commit d40d23b233f0b2e6fc25937f1632ac5b9d4f61e5)