* Add cancellable argument to g_tls_interaction_ask_password
and g_tls_interaction_ask_password_async.
* This is API breakage, but this API has not yet been released
in a stable release (and very unlikely used yet).
* Since we're breaking unreleased API, expand amount of padding
on GTlsInteractionClass because we're going to need it.
https://bugzilla.gnome.org/show_bug.cgi?id=656443
The database is an abstract object implemented by the various TLS
backends, which is used by GTlsConnection to lookup certificates
and keys, as well as verify certificate chains.
Also add GTlsInteraction, which can be used to prompt the user
for a password or PIN (used with the database).
https://bugzilla.gnome.org/show_bug.cgi?id=636572
