To help in slowly migrating the merge code to the tree processor, create a
tee implementation of the tee processor that sends everything to two
processors.

* subversion/include/private/svn_diff_tree.h
  (svn_diff_tree_processor_t): Fix indentation of dir_changed arguments.
  (svn_diff__tree_processor_tee_create): New function.

* subversion/libsvn_diff/diff_tree.c
  (tee_baton_t): New struct.
  (tee_node_baton_t): New struct.

  (tee_*): New functions. Wrapping two processors to one.
  (svn_diff__tree_processor_tee_create): New function.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1440354 13f79535-47bb-0310-9956-ffa450edef68