Fix Issue #2491 Add --dry-run flag to "svn update" client command

HEADERS AND DEPRECATIONS

* subversion/include/svn_client.h
  (svn_client_update4) : Modify signature and document it.

* subversion/libsvn_client/deprecated.c
  (svn_client_update3)        : Fix call of svn_client_update4 to pass
                                FALSE to dry_run.
* subversion/include/svn_wc.h
  (svn_wc_crawl_revisions5,
   svn_wc_get_update_editor4) : Modify signature and document it.

* subversion/libsvn_wc/deprecated.c
  (svn_wc_crawl_revisions4)   : Call svn_wc_crawl_revisions5 with dry_run
                                as FALSE.
  (svn_wc_get_update_editor3) : Call svn_wc_get_update_editor4 with dry_run
                                as FALSE.

* subversion/libsvn_client/client.h
  (svn_client__update_internal) : Modify signature and document it.

IMPLEMENTATION

* subversion/svn/main.c
  (svn_cl__cmd_table): Let update accept opt_dry_run.
  (main)             : Don't allow opt_dry_run with --set-depth and --parents.

* subversion/libsvn_client/update.c
  (update_internal)             : Accept dry_run.
                                  Fix call of svn_wc_get_update_editor4,
                                  svn_wc_crawl_revisions5.
                                  Avoid handling externals.

  (svn_client__update_internal) : Accept dry_run.
                                  Fix calls of update_internal.
  (svn_client_update4)          : Accept dry_run. 
                                  Fix call of svn_client__update_internal.

* subversion/svn/update-cmd.c
  (svn_cl__update): Fix call of svn_client_update4.

* subversion/libsvn_wc/update_editor.c
  (edit_baton)                      : Added a svn_boolean_t dry_run.
                                      Added a apr_hash_t dry_run_deletions.
  (remember_dry_run_deletion)       : New function to keep track of 
                                      dry run deletions
  (complete_directory, open_root,
   do_entry_deletion, add_directory,  
   open_directory, close_directory,
   absent_file_or_dir, add_file,
   open_file, apply_textdelta,
   merge_file, close_file,
   tweak_entries, close_edit)       : Implemented dry-run logic.

   (make_editor)                    : Accept dry_run and initialize dry_run
                                      and dry_run_deletions.
   (svn_wc_get_update_editor4,
    svn_wc_get_switch_editor4)      : Fix call of make_editor.


* subversion/libsvn_wc/adm_crawler.c
  (restore_node)                    : Accept dry_run and if TRUE, do only
                                      notification without restoring the node.

  (report_revisions_and_depths)     : Accept dry_run and fix call of 
                                      restore_node and recursive call of
                                      report_revisions_and_depths.

  (svn_wc_crawl_revisions5)         : Accept dry_run and fix call of
                                      restore_node and recursive call of
                                      svn_wc_crawl_revisions5.
* subversion/libsvn_client/switch.c
  (switch_internal) : Fix call of svn_wc_crawl_revisions5.

* subversion/libsvn_client/status.c
  (svn_client_status5) : Fix call of svn_wc_crawl_revisions5.

* subversion/libsvn_client/diff.c
  (diff_repos_wc) : Fix call of svn_wc_crawl_revisions5.

* subversion/libsvn_client/checkout.c
  (svn_client__checkout_internal) : Fix call of svn_client__update_internal.

* subversion/libsvn_client/externals.c
  (switch_dir_external) : Fix call of svn_client__update_internal.


TEST SUITE

* subversion/tests/cmdline/svntest/actions.py
  (_post_update_checks)  : New function to do the checks after an update.
  (run_and_verify_update): Accept a dry_run parameter. If TRUE, check that 
                           the dry run hasn't affected the wc.

* subversion/tests/cmdline/changelist_tests.py
  subversion/tests/cmdline/externals_tests.py
  subversion/tests/cmdline/prop_tests.py
  subversion/tests/cmdline/update_tests.py
  subversion/tests/cmdline/resolved_tests.py
  subversion/tests/cmdline/trans_tests.py
  subversion/tests/cmdline/switch_tests.py
  subversion/tests/cmdline/stat_tests.py
  subversion/tests/cmdline/depth_tests.py

  (Tests) : Fix callers of run_and_verify_update.

Patch by: Arwin Arni <arwin{_AT_}collab.net>
Guided by kameshj