add a test for casecmp with sjis string.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@14142 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

bootstraptest/test_knownbug.rb

@@ -56,3 +56,10 @@ assert_equal 'ok', %q{
     :ok
   end
 }
+
+assert_equal 'ok', %q{
+  s1 = "\x81\x41".force_encoding("sjis")
+  s2 = "\x81\x61".force_encoding("sjis")
+  s1.casecmp(s2) ? :ng : :ok
+}
+