implement equals

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/compress/branches/compress-2.0@1556201 13f79535-47bb-0310-9956-ffa450edef68
porting the ArArchiveEntry is easy - as expected

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/compress/branches/compress-2.0@1556202 13f79535-47bb-0310-9956-ffa450edef68