test: commentary for [h-m]*.go

R=golang-dev, gri
CC=golang-dev
https://golang.org/cl/5674112
diff --git a/test/indirect.go b/test/indirect.go
index df8d3c7..bb20f30 100644
--- a/test/indirect.go
+++ b/test/indirect.go
@@ -4,6 +4,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Test various safe uses of indirection.
+
 package main
 
 var m0 map[string]int