Improve API.
Improve API.

* subversion/bindings/swig/ruby/svn/fs.rb
  (Svn::Fs::FileSystem.create,
   Svn::Fs::FileSystem.open): Make config argument optional.


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@863106 13f79535-47bb-0310-9956-ffa450edef68

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