On the 'move-tracking-2' branch: Calculate branch root path on demand rather
than storing it, as it can change during the edit and was not being updated.

* subversion/include/private/svn_editor3.h,
  subversion/libsvn_delta/branching.c
  (svn_branch_instance_t): Store the outer branch and outer-branch eid
    instead of the branch root path.
  (svn_branch_instance_create): Change the constructor parameters in the
    same way.
  (svn_branch_get_root_rrpath): Calculate the result by recursion. Add a
    result pool parameter.
  Update all callers.

* subversion/libsvn_delta/compat3b.c
  Update all callers.

* subversion/svnmover/svnmover.c
  Update all callers.


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/move-tracking-2@1639611 13f79535-47bb-0310-9956-ffa450edef68