code review 7235081: cmd/gc: put 'not used' message on correct line

test/fixedbugs/bug357.go

 // errorcheck
 
 // Copyright 2011 The Go Authors.  All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 // issue 1993.
 // error used to have last line number in file
 
 package main
 
 func bla1() bool {
         return false
 }
 
 func bla5() bool {
         _ = 1
-        false  // ERROR "false not used|value computed is not used"
+        false  // ERROR "false evaluated but not used|value computed is not used"
         _ = 2
         return false
 }
 
 func main() {
         x := bla1()
         _ = x
 }