text: Fix the default value of "editable"

The "editable" property is documented to default to TRUE, but is
initialized to FALSE in the _init() function.

Third party code would be affected if we changed the default to be
TRUE, so we have to change the default value in the GParamSpec.

https://bugzilla.gnome.org/show_bug.cgi?id=654726

clutter/clutter-text.c

@@ -2863,7 +2863,7 @@ clutter_text_class_init (ClutterTextClass *klass)
   pspec = g_param_spec_boolean ("editable",
                                 P_("Editable"),
                                 P_("Whether the text is editable"),
-                                TRUE,
+                                FALSE,
                                 G_PARAM_READWRITE);
   obj_props[PROP_EDITABLE] = pspec;
   g_object_class_install_property (gobject_class, PROP_EDITABLE, pspec);