cmd/5l etc: restore comments lost during C -> Go conversion

It appears that c2go dropped comments inside struct { ... } and enum { ... }.
Restore them.

Identified missing comments by checking for comments present
in the C code but not the Go code, made a list, and then reapplied
with some mechanical help.

Missing comment finder: http://play.golang.org/p/g6qNUAo1Y0

Change-Id: I323ab45c7ef9d51e28eab3b699eb14bee1eef66b
Reviewed-on: https://go-review.googlesource.com/6899
Reviewed-by: Rob Pike <r@golang.org>

src/cmd/internal/gc/range.go

@@ -135,6 +135,13 @@ out:
 }
 
 func walkrange(n *Node) {
+	// variable name conventions:
+	//	ohv1, hv1, hv2: hidden (old) val 1, 2
+	//	ha, hit: hidden aggregate, iterator
+	//	hn, hp: hidden len, pointer
+	//	hb: hidden bool
+	//	a, v1, v2: not hidden aggregate, val 1, 2
+
 	t := n.Type
 
 	a := n.Right