qt: Add genpin suppport
* pinentry/pinentry.c (pinentry_inq_genpin): New. Based on inq_quality. (cmd_setgenpin_tt, cmd_setgenpin_label): New string helpers. (register_commands): Register stringhelper commands. * pinentry/pinentry.h (struct pinentry): Add new variables for label and tooltips. * qt/main.cpp (qt_cmd_handler): Set up labels. * qt/pinentrydialog.cpp (PinEntryDialog::PinEntryDialog): Add generate action if label is provided. (PinEntryDialog::setGenpinLabel): New. (PinEntryDialog::setGenpinTT): New. (PinEntryDialog::textChanged): Hide generate action if text is entered. (PinEntryDialog::generatePin): Inquire generate. (PinEntryDialog::toggleVisibility): Allow calls from other senders.
This adds some basic support to have gpg-agent generate a
passphrase. This helps espcially in the symmetric encryption
use case. It could be nicer of course how we present the
generated pin regarding printing etc but it is better then nothing.
It also gives us future options to improve the GENPIN
in the gpg-agent without changes to pinentry.