Add the GLIB_AVAILABLE_IN_ALL annotation to all old functions (that
haven't already been annotated with the GLIB_AVAILABLE_IN_* macros or a
deprecation macro).
If we discover in the future that we cannot use only one macro on
Windows, it will be an easy sed patch to fix that.
https://bugzilla.gnome.org/show_bug.cgi?id=688681
Implement an extension point for proxy protocol implementation. This
is mainly useful for socket-based proxy where it is possible to use the
proxied socket the same way it would for other stream based socket.
Reviewed-by: Dan Winship <danw@gnome.org>