Fix code to support Ruby 1.9.1 or later, and to pass all tests except for ones related to bugs of Ripper.

Fix RubyBuilder to deal with change of event name from on_body_stmt to on_bodystmt, from on_xstring_new to on_regexp_new and from on_xstring_add to on_regexp_add.
Fix Ruby::List class to deal with an issue of flatten.
Fix Traversal to call args? method with correct arguments.
Fix traversal.rb to have correct indent.