Make svnpredumpfilter.py detect copies of copies (of copies...)
and include them in the set of required paths.

* tools/server-side/svnpredumpfilter.py
  (DependencyTracker.__init__): Use sets instead of lists to store
   the sets of included paths and dependent paths.
  (DependencyTracker.path_incldued): Use union of sets instead of
   list concatenation.
  (DependencyTracker.handle_changes): Rename to ...
  (DependencyTracker.include_missing_copies): ... this, and repeatedly
   cross-check all included and dependent paths with all copies to find
   more dependent paths to add until no more relevant copies can be found.
  (svn_log_stream_get_dependencies): Handle rename of method.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1626182 13f79535-47bb-0310-9956-ffa450edef68