docs: Add reference to useful GObject tutorial

Add a reference to a GObject tutorial which
is a good introduction to the various macros etc.
and what they're for.

diff --git a/doc/cookbook/actors.xml b/doc/cookbook/actors.xml
index 1a307f0..c1fc63f 100644 (file)
--- a/doc/cookbook/actors.xml
+++ b/doc/cookbook/actors.xml
@@ -72,7 +72,9 @@
         heavily on GObject concepts and idioms. If you are unfamiliar with
         GObject, please read
         <ulink url="http://library.gnome.org/devel/gobject/unstable/">the GObject
-        Reference Manual</ulink> before proceeding.</para>
+        Reference Manual</ulink> before proceeding. You might also find
+        <ulink url="http://diuf.unifr.ch/pai/wiki/doku.php/research:projects:gobject_tutorial">this
+        tutorial</ulink> a useful introduction.</para>
       </tip>
 
       <para>The code for this solution is structured like standard GObject