Update some obsolete comments.

Fix a few stray references to expression eval functions that don't
exist anymore or don't take the same input representation they used to.

src/backend/optimizer/util/clauses.c

@@ -354,8 +354,8 @@ make_and_qual(Node *qual1, Node *qual2)
 }
 
 /*
- * Sometimes (such as in the input of ExecQual), we use lists of expression
- * nodes with implicit AND semantics.
+ * The planner frequently prefers to represent qualification expressions
+ * as lists of boolean expressions with implicit AND semantics.
  *
  * These functions convert between an AND-semantics expression list and the
  * ordinary representation of a boolean expression.

src/backend/utils/cache/relcache.c

@@ -4743,7 +4743,7 @@ RelationGetIndexExpressions(Relation relation)
  * RelationGetIndexPredicate -- get the index predicate for an index
  *
  * We cache the result of transforming pg_index.indpred into an implicit-AND
- * node tree (suitable for ExecQual).
+ * node tree (suitable for use in planning).
  * If the rel is not an index or has no predicate, we return NIL.
  * Otherwise, the returned tree is copied into the caller's memory context.
  * (We don't want to return a pointer to the relcache copy, since it could

src/pl/plpgsql/src/pl_exec.c

@@ -4759,7 +4759,7 @@ exec_assign_value(PLpgSQL_execstate *estate,
 				 * fixed-length array types we skip the assignment.  We can't
 				 * support assignment of a null entry into a fixed-length
 				 * array, either, so that's a no-op too.  This is all ugly but
-				 * corresponds to the current behavior of ExecEvalArrayRef().
+				 * corresponds to the current behavior of execExpr*.c.
 				 */
 				if (arrayelem->arraytyplen > 0 &&		/* fixed-length array? */
 					(oldarrayisnull || isNull))