Add _g_io_module_get_default(), which implements the
figure-out-the-best-available-module-that-is-actually-usable logic,
and use that to simplify g_proxy_resolver_get_default(),
g_settings_backend_get_default(), g_tls_backend_get_default(), and
g_vfs_get_default().
https://bugzilla.gnome.org/show_bug.cgi?id=620932
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
This adds an extension point for TLS connections to gio, with a
gnutls-based implementation in glib-networking.
Full TLS support is still a work in progress; the current API is
missing some features, and parts of it may still be changed before
2.28.
https://bugzilla.gnome.org/show_bug.cgi?id=588189
