Remove more code that was duplicated for diff and summarized diff from
libsvn_client, by moving the writer settings up a level and reusing the
now identical driver code.

* subversion/libsvn_client/diff.c
  (do_diff): Move diff tranforms to both callers. Add text_deltas boolean.
  (do_diff_summarize): Remove function.

  (svn_client_diff6,
   svn_client_diff_peg6): Apply diff transforms here (while setting up the
     writer).

  (svn_client_diff_summarize2,
   svn_client_diff_summarize_peg2): Setup summarize processor and call
     do_diff().


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1569945 13f79535-47bb-0310-9956-ffa450edef68