Fix up test failure on Ruby 1.8.*
Fix up test failure on Ruby 1.8.*

increments/libxml-ruby,sferik/libxml-ruby,increments/libxml-ruby,sferik/libxml-ruby,sferik/libxml-ruby,xml4r/libxml-ruby,xml4r/libxml-ruby,sferik/libxml-ruby,xml4r/libxml-ruby,sferik/libxml-ruby,sferik/libxml-ruby,increments/libxml-ruby