also modifications for better coderange detection
* test/ruby/test_unicode_escapes.rb: test cases
* test/ruby/test_mixed_unicode_escapes.rb: mixed encoding test cases
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@13836 b2dd03c8-39d4-4d8f-98ff-823fe69b080e