Import a package renamed copy of Commons Codec with just those bits required for Base64 encoding/decoding

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1459218 13f79535-47bb-0310-9956-ffa450edef68
Add the ability to decode a subset of a byte array as this will enable Tomcat to use the decoder more efficiently.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1459223 13f79535-47bb-0310-9956-ffa450edef68