swig-pl: Modernize the SYNOPSIS example and talk about canonicalization.

* subversion/bindings/swig/perl/native/Client.pm
  (SYNOPSIS): Use a more modern example that fully sets up authentication in a
    way that matches the command line client.  Also canonicalize the target
    before passing it into the APIs.
  (PARAMETER NOTES): Talk about canonicalization.

Suggested by: Anton Yuzhaninov <citrin+svn{_AT_}citrin.ru>
(at least the notion that our documentation should mention canonicalization)


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1566230 13f79535-47bb-0310-9956-ffa450edef68