Porting r161115,-71,-80 from FSFS to FSX.

* subversion/libsvn_fs_x
  (): Update mergeinfo.

* subversion/libsvn_fs_x/transaction.c
  (replace_change): Remove this function.
  (path_change_dup): Introduce this new copy utility.
  (fold_change): Take all code from FSFS.
  (process_changes): Prodide the temporary deletions container.

* subversion/tests/libsvn_fs/fs-test.c
  (test_delete_replaced_paths_changed): This works with all backends now.

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1631184 13f79535-47bb-0310-9956-ffa450edef68