cookbook: Added ClutterScript example

Added a simple script and program to load it, to support
recipe on ClutterScript for UI definitions.

Also amended the Makefile (following the pattern of
the tests/interactive Makefile) to enable signal
connection from ClutterScript by passing -export-dynamic
to linker.

doc/cookbook/examples/script-ui.c

@@ -0,0 +1,69 @@
+#include <stdlib.h>
+#include <clutter/clutter.h>
+
+gboolean
+_pointer_motion_cb (ClutterActor *actor,
+                    ClutterEvent *event,
+                    gpointer      user_data)
+{
+  g_debug ("Pointer movement");
+  return TRUE;
+}
+
+void
+_button_clicked_cb (ClutterClickAction *action,
+                    ClutterActor       *actor,
+                    gpointer            user_data)
+{
+  /* get the UI definition passed to the handler */
+  ClutterScript *ui = CLUTTER_SCRIPT (user_data);
+
+  ClutterState *transitions;
+
+  clutter_script_get_objects (ui,
+                              "transitions", &transitions,
+                              NULL);
+
+  clutter_state_set_state (transitions, "faded-in");
+}
+
+int
+main (int argc, char *argv[])
+{
+  g_thread_init (NULL);
+
+  clutter_init (&argc, &argv);
+
+  /* path to the directory containing assets (e.g. images) for the script to load */
+  const gchar *paths[] = { TESTS_DATA_DIR };
+
+  ClutterScript *ui = clutter_script_new ();
+  clutter_script_add_search_paths (ui, paths, 1);
+
+  gchar *filename = "script-ui.json";
+  GError *error = NULL;
+
+  clutter_script_load_from_file (ui, filename, &error);
+
+  if (error != NULL)
+    {
+      g_critical ("Error loading ClutterScript file %s\n%s", filename, error->message);
+      g_error_free (error);
+      exit (EXIT_FAILURE);
+    }
+
+  ClutterActor *stage;
+
+  clutter_script_get_objects (ui,
+                              "stage", &stage,
+                              NULL);
+
+  /* make the objects in the script available to all signals */
+  clutter_script_connect_signals (ui, ui);
+
+  clutter_actor_show (stage);
+
+  clutter_main ();
+
+  return EXIT_SUCCESS;
+}