[FILEUPLOAD-229] If an actual lower/upper case is required, then should use a fixed locale (unless the code is intended to use the default locale, which is quite unusual for Commons).
A suitable locale is Locale.ENGLISH as that behaves well with ASCII and ISO-8859-1.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/fileupload/trunk@1455868 13f79535-47bb-0310-9956-ffa450edef68