fix javadoc errors detected by Java8 EA b120

Not there are still 54 errors as the "unknown" JCIP tags cause trouble
but I neither want to remove them nor add a dependency just to make a
broken tool happy.


git-svn-id: https://svn.apache.org/repos/asf/commons/proper/compress/trunk@1552970 13f79535-47bb-0310-9956-ffa450edef68