Avoid index rebuild for no-rewrite ALTER TABLE .. ALTER TYPE.

Noah Misch.  Review and minor cosmetic changes by me.

src/include/nodes/parsenodes.h

@@ -2062,6 +2062,7 @@ typedef struct IndexStmt
 	Node	   *whereClause;	/* qualification (partial-index predicate) */
 	List	   *excludeOpNames; /* exclusion operator names, or NIL if none */
 	Oid			indexOid;		/* OID of an existing index, if any */
+	Oid			oldNode;		/* relfilenode of my former self */
 	bool		unique;			/* is index unique? */
 	bool		primary;		/* is index on primary key? */
 	bool		isconstraint;	/* is it from a CONSTRAINT clause? */