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
Add GNetworkMonitor and its associated extension point, provide a base
implementation that always claims the network is available, and a
netlink-based implementation built on top of that that actually tracks
the network state.
https://bugzilla.gnome.org/show_bug.cgi?id=620932