Partial fix for Issue #443: post-commit hook script (error) output lost
   This is step 5 : Replace all usage of svn_commit_callback_t with
   svn_commit_callback2_t.

   * subversion/libsvn_ra/wrapper_template.h
     (compat_get_commit_editor): Modified to use
      svn_compat_wrap_commit_callback.

   * subversion/libsvn_ra/ra_loader.c
     (include): svn_types.h
     (svn_ra_get_commit_editor2): New function using svn_commit_callback2_t.
     (svn_ra_get_commit_editor): Modified to use svn_ra_get_commit_editor2.

   * subversion/libsvn_ra/ra_loader.h
     (svn_ra__vtable_t): Modified the get_commit_editor member to use
      svn_commit_callback2_t instead of svn_commit_callback_t.

   * subversion/include/svn_repos.h
     (svn_repos_get_commit_editor4): New version of svn_repos_get_commit_editor3
      to use svn_commit_callback2_t.
     (svn_repos_get_commit_editor3): Deprecated.

   * subversion/include/svn_types.h
     (svn_commit_info_dup): New API to perform deep-copy for the
      svn_commit_info_t structure.
     (svn_commit_callback2_t): New callback similar to svn_commit_callback_t
      but using the svn_commit_info_t structure.
     (svn_commit_callback_t): Deprecated.
     (svn_compat_wrap_commit_callback): New API to wrap commit_baton
      and provide a svn_commit_callback_t type callback.

   * subversion/include/svn_ra.h
     (svn_ra_get_commit_editor2): New version of svn_ra_get_commit_editor
      using svn_commit_callback2_t.
     (svn_ra_get_commit_editor): Deprecated.

   * subversion/libsvn_subr/constructors.c
     (svn_commit_info_dup): New function to deep copy the svn_commit_info_t
      structure.
    
   * subversion/libsvn_subr/compat.c: New file to provide compatibility
     for deprecated callback types.
     (commit_wrapper_baton): New structure to wrap commit baton and
      the svn_commit_callback_t callback.
     (commit_wrapper_callback): Wrapper callback that translates call of
      svn_commit_callback2_t to svn_commit_callback_t.
     (svn_compat_wrap_commit_callback): New function to wrap commit_baton
      and provide a svn_commit_callback_t type callback.

   * subversion/libsvn_ra_local/ra_plugin.c
     (deltify_etc_baton): Modified to use svn_commit_callback2_t.
     (deltify_etc): Now uses the svn_commit_callback2_t signature
      and callbacks.
     (svn_ra_local__get_commit_editor): Modified to use
      svn_client_commit_callback2_t.

   * subversion/libsvn_client/delete.c
     (delete_urls): Use svn_ra_get_commit_editor2 instead of
      svn_ra_get_commit_editor.

   * subversion/libsvn_client/client.h
     (svn_client__commit_callback): Modified to use svn_commit_info_t
      instead of individual commit info parameters.

   * subversion/libsvn_client/copy.c
     (repos_to_repos_copy): Use svn_ra_get_commit_editor2 instead of
      svn_ra_get_commit_editor.
     (wc_to_repos_copy): Use svn_ra_get_commit_editor2 instead of
      svn_ra_get_commit_editor.

   * subversion/libsvn_client/commit_util.c
     (svn_client__commit_callback): Modified function to use
      svn_commit_info_t.

   * subversion/libsvn_client/add.c
     (mkdir_urls): Use svn_ra_get_commit_editor2 instead of
      svn_ra_get_commit_editor.

   * subversion/libsvn_client/commit.c
     (get_ra_editor): Modified to use svn_ra_get_commit_editor2.

   * subversion/tests/libsvn_repos/repos-test.c
     (commit_editor_authz): Modified to use svn_repos_get_commit_editor4.

   * subversion/libsvn_repos/commit.c
     (edit_baton): Now uses svn_commit_callback2_t.
     (close_edit): Use svn_commit_callback2_t based callback.
     (svn_repos_get_commit_editor4): New API to use
      svn_commit_callback2_t.
     (svn_repos_get_commit_editor3): Modified to wrap around the
      svn_repos_get_commit_editor4 function.
     (svn_repos_get_commit_editor2): Modified to wrap around the
      svn_repos_get_commit_editor3 function.
     (svn_repos_get_commit_editor): Modified to wrap around the
      svn_repos_get_commit_editor2 function.

   * subversion/libsvn_ra_svn/client.c
     (ra_svn_commit_callback_baton_t): Now uses svn_commit_callback2_t.
     (ra_svn_end_commit): Modified to use commit_info.
     (ra_svn_commit): Modified to use svn_commit_callback2_t.

   * subversion/libsvn_ra_dav/ra_dav.h
     (svn_ra_dav__get_commit_editor): Modified to use
      svn_commit_callback2_t.

   * subversion/libsvn_ra_dav/commit.c
     (commit_ctx_t): Modified to use svn_commit_callback2_t.
     (commit_close_edit): Modified to use svn_commit_info.
     (svn_ra_dav__get_commit_editor): Modifed to use
      svn_commit_callback2_t.

   * subversion/svnserve/serve.c
     (commit_done): Modified to use svn_commit_info_t.
     (commit): Modified to use svn_repos_get_commit_editor4.