Add a G_DEFINE_QUARK macro

https://bugzilla.gnome.org/show_bug.cgi?id=627240

glib/gquark.c

@@ -92,6 +92,18 @@ static gint           quark_block_offset = 0;
  * particular string. A GQuark value of zero is associated to %NULL.
  **/
 
+/**
+ * G_DEFINE_QUARK:
+ * @QN: the string to return a #GQuark for
+ * @q_n: prefix for the function name
+ *
+ * A convenience macro which defines a function returning the
+ * #GQuark for the string @QN. The function will be named
+ * @q_n<!-- -->_quark().
+ *
+ * Since: 2.34
+ */
+
 /**
  * g_quark_try_string:
  * @string: (allow-none): a string.