In the repos-wc diff handling: verify the expected checksum and simplify
some base handling in close_file.

* subversion/libsvn_wc/diff_editor.c
  (file_baton_t): Add base props and the raw checksum data.
  (open_file): Obtain the base-props.
  (window_handler_baton): Remove struct.
  (window_handler): Remove function.
  (apply_textdelta): Verify expected checksum. Directly hook libsvn_delta's
    window handler as the stream wrappers can do all our work.
  (close_file): Parse result hash here. Use base checksum as cached.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1444985 13f79535-47bb-0310-9956-ffa450edef68