Tests on our AS/400 shows the value to be "OS/400".

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/lang/trunk@1565487 13f79535-47bb-0310-9956-ffa450edef68
Better name.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/lang/trunk@1565488 13f79535-47bb-0310-9956-ffa450edef68