Add a pattern id variable to all nodes.

include/pattern.h

@@ -52,6 +52,10 @@ struct pattern_node_s {
    * The id is unique within the pattern.
    */
   int id;
+  /**
+   * The id of the pattern that this node belongs to.
+   */
+  int pattern_id;
 
   /**
    * The node's data that varies based on type.
@@ -122,16 +126,6 @@ struct pattern_node_s {
        */
       struct pattern_node_s* right;
     } fork_s;
-
-    /**
-     * Data for an "end" node.
-     */
-    struct {
-      /**
-       * The ID of the pattern that just finished matching.
-       */
-      int pattern_id;
-    } end_s;
   } data_u;
 };