Support svn_ra_get_commit_editor3().
Support svn_ra_get_commit_editor3().

* subversion/bindings/swig/ruby/svn/ra.rb
  (Svn::Ra::Session#commit_editor2): Use Svn::Ra.get_commit_editor3
  instead of Svn::Ra.get_commit_editor2.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion