Cast NULL to (char *) in vararg apr_pstrcat call.

* subversion/libsvn_delta/compat.c
  (apply_change): here

* subversion/libsvn_fs/editor.c
  (FSPATH): here
 
* subversion/libsvn_fs_fs/caching.c
  (svn_fs_fs__initialize_caches): here
 
* subversion/libsvn_ra_serf/util_error.c
  (svn_ra_serf__wrap_err): here

* subversion/libsvn_repos/commit.c
  (ev2_check_authz): here
 
* subversion/libsvn_subr/config.c
  (get_category_config): here

* subversion/libsvn_subr/dirent_uri.c
  (svn_uri_get_dirent_from_file_url,
   svn_uri_get_file_url_from_dirent): here
 
* subversion/libsvn_subr/error.c
  (svn_error_wrap_apr): here

* subversion/libsvn_subr/io.c
  (svn_io_run_diff3_3): here

* subversion/libsvn_subr/named_atomic.c
  (svn_atomic_namespace__create,
   svn_atomic_namespace__cleanup): here

* subversion/libsvn_subr/sysinfo.c
  (debian_release): here
 
* subversion/mod_dav_svn/authz.c
  (dav_svn__allow_read): here

* subversion/mod_dav_svn/repos.c
  (deliver): here

* subversion/svn/info-cmd.c
  (print_info_xml): here

* subversion/svnauth/svnauth.c
  (subcommand_help): here


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1535070 13f79535-47bb-0310-9956-ffa450edef68