Fixes #4093.
R=golang-dev, bradfitz, r
CC=golang-dev
https://golang.org/cl/
6536047
// integer values.
type byte byte
-// rune is an alias for int and is equivalent to int in all ways. It is
+// rune is an alias for int32 and is equivalent to int32 in all ways. It is
// used, by convention, to distinguish character values from integer values.
-// In a future version of Go, it will change to an alias of int32.
type rune rune
// Type is here for the purposes of documentation only. It is a stand-in