added comment to explain list_lookup()

include/list.h

@@ -63,6 +63,13 @@ void list_push(struct list *l, void *p);
 void list_remove(struct list *l, void *p);
 
 /** Search the list for an element whose first element is a character array which matches name.
+ *
+ * List elements should be of the following form:
+ *
+ * struct obj {
+ *    char *name;
+ *    // more members
+ * }
  *
  * @see Only possible because of §1424 of http://c0x.coding-guidelines.com/6.7.2.1.html
  */