Improve GNetworkMonitor docs

Make sure we get signal and property docs, and mention
the extension point in the overview.

docs/reference/gio/gio.types

@@ -56,6 +56,7 @@ g_mount_get_type
 g_mount_operation_get_type
 g_native_volume_monitor_get_type
 g_network_address_get_type
+g_network_monitor_get_type
 g_network_service_get_type
 g_output_stream_get_type
 g_permission_get_type

docs/reference/gio/overview.xml

@@ -81,8 +81,9 @@
           <listitem><para>stores and retrieves application settings</para></listitem>
        </varlistentry>
     </variablelist>
-    There is support for network programming, including name resolution, lowlevel socket
-    APIs and highlevel client and server helper classes:
+    There is support for network programming, including connectivity monitoring,
+    name resolution, lowlevel socket APIs and highlevel client and server
+    helper classes:
     <variablelist>
        <varlistentry>
           <term>GSocket</term>
@@ -104,6 +105,10 @@
           <term>GSocketConnection</term>
           <listitem><para>network connection stream</para></listitem>
        </varlistentry>
+       <varlistentry>
+          <term>GNetworkMonitor</term>
+          <listitem><para>network connectivity monitoring</para></listitem>
+       </varlistentry>
     </variablelist>
     There is support for connecting to <link linkend="http://www.freedesktop.org/wiki/Software/dbus">D-Bus</link>,
     sending and receiving messages, owning and watching bus names,
@@ -550,7 +555,6 @@
        point based on libproxy.
      </para>
    </formalpara>
-
    <formalpara>
      <title>G_TLS_BACKEND_EXTENSION_POINT_NAME</title>
 
@@ -565,5 +569,20 @@
      </para>
    </formalpara>
 
+   <formalpara>
+     <title>G_NETWORK_MONITOR_EXTENSION_POINT_NAME</title>
+
+     <para>
+       Allows to provide implementations for network connectivity
+       monitoring.
+       Implementations of this extension point must implement
+       the #GNetworkMonitorInterface interface.
+     </para>
+     <para>
+       GIO contains an implementation of this extension point
+       that is using the netlink interface of the Linux kernel.
+     </para>
+   </formalpara>
   </chapter>
 </part>
+