DBusInterfaceInfo.cacheBuild

Builds a lookup-cache to speed up g_dbus_interface_info_lookup_method(), g_dbus_interface_info_lookup_signal() and g_dbus_interface_info_lookup_property().

If this has already been called with @info, the existing cache is used and its use count is increased.

Note that @info cannot be modified until g_dbus_interface_info_cache_release() is called.