Minor tweaks to simplify and strengthen some diff code.
Minor tweaks to simplify and strengthen some diff code.

* subversion/libsvn_client/repos_diff.c
  (make_file_baton): Require the correct pointer type for the edit baton
    argument, because we can, just like in make_dir_baton().
  (diff_deleted_dir): Declare and assert that the supplied revision number
    is valid, because we don't need to handle invalid numbers.

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