[CODEC-174] Small (2.3%) but consistent performance gain with this patch from https://issues.apache.org/jira/secure/attachment/12612838/CODEC-174-delete-subsequence-cache-and-use-String.patch. The nicer aspect of the patch is that it simplifies the code.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/codec/trunk@1541231 13f79535-47bb-0310-9956-ffa450edef68