Version 3: Patch to fix issue 2069 - "svn status" in xml mode

* subversion/include/svn_wc.h
  (enum svn_wc_notify_action_t): added new notification
  'svn_wc_notify_status_xml_completed', which will be
  last notification for status xml

* subversion/include/svn_client.h
  (svn_client_status3): prototype added for new public interface
  function

* subversion/libsvn_client/delete.c
  (svn_client__can_delete): using new wrapper function 
  svn_client_status3

* subversion/libsvn_client/externals.c
  (svn_client__do_external_status): using new wrapper function
  svn_client_status3

* subversion/libsvn_client/status.c
  (svn_client_status3): added new public interface function
  which support both traditional and xml output and will wrap the 
  eariler function 'svn_client_status2'
  (svn_client_status2): Calls new svn_client_status3 with xml 
  parameter as FALSE

* subversion/clients/cmdline/cl.h
  (svn_cl__print_status): added new argument 'xml_mode' to prototype

* subversion/clients/cmdline/status.c
  (print_statents_xml): added new function to print status in
  xml format to standard console
  (print_status): added new argument 'xml_mode' and 
  checking this argument to decide which format for status output 
  (svn_cl__print_status_xml): added new argument 'xml_mode'
   and passes it to print_status function

* subversion/clients/cmdline/notify.c
  (notify): 'svn_wc_notify_status_xml_completed' is called 
  as the last status notification and prints out the 'Status
  against revision' in xml mode, only for 'svn status -u' option

* subversion/clients/cmdline/main.c
  (svn_cl__cmd_table[]): added --xml and --incremental options 
   in to subcommand array for status subcommand

* subversion/clients/cmdline/status-cmd.c
  (struct status_baton): added new item 'xml_mode' in struct
  for storing xml mode is requested or not
  (print_header_xml): prints xml header
  (print_footer_xml): prints xml footer
  (print_status): calls svn_cl__print_status function with
  new parameter xml_mode
  (svn_cl__status): checks for xml option and decides
  which respective callback functions for xml or ordinary
  output. Also prints xml header and footer

* subversion/clients/cmdline/dtd/status.dtd
  added a new dtd file for validating status xml

* subversion/tests/clients/cmdline/stat_tests.py
  (status_in_xml): new function to verify success when
  svn status output in xml format
  (test_list): added status_in_xml