Reduce the memory used by svn_repos_get_logs3 invocations that pass many arguments.
Reduce the memory used by svn_repos_get_logs3 invocations that pass
many arguments.

This improves the situation noted in issue #2494, but does not fix
the whole thing.

* subversion/libsvn_repos/log.c
  (path_history_root): Removed.
  (path_info): Remove the root member, it is no longer needed.
  (svn_repos_get_logs3): Create a single rev root instead of making
   one per path.  Inline the authz check that used to happen inside
   path_history_root, which no longer exists.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion