Very many testcases, some GLib tools (resource compiler, etc) and
GApplication were calling g_type_init().
Remove those uses, as they are no longer required.
https://bugzilla.gnome.org/show_bug.cgi?id=686161
make sure the proxy threads are in the "waiting for a connection"
state when we do the final cleanup, or else there are race conditions
involving which thread processes the GCancellable cancellation first.
Rather than depending on the host's DNS configuration to properly
return an error for a non-existent hostname, just substitute in
a dummy GResolver implementation that does it for us.
