Improve API.
Improve API.

* subversion/bindings/swig/ruby/svn/ra.rb (Svn::Ra::Session.open):
  Use nil for default config parameter value instead of an empty Hash.


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@867079 13f79535-47bb-0310-9956-ffa450edef68

wbond/subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion