[n.compilation] Don't use locking macro

Until http://dev.clojure.org/jira/browse/CLJ-1472 is resolved, `locking`
won't work on ART. For now, we just hope that noone will call
`clear-cache` explicitly, all the more so call it from multiple threads.
Remove surplus copyright notices

Because I hate them. I left only the ones put by Daniel in the
namespaces where there is still code written by him.