[CODEC-168] Reported by Daniel Cassidy: Add DigestUtils.updateDigest(MessageDigest, InputStream). No need for additional tests as the method is used by Codec itself.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/codec/trunk@1462710 13f79535-47bb-0310-9956-ffa450edef68