compress/bzip2: use io.ByteReader instead of internal interface
compress/bzip2: use io.ByteReader instead of internal interface

R=golang-dev, bradfitz
CC=golang-dev
http://codereview.appspot.com/6663044
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go