Fix removing unexpected control chars

`cc` is created as `"\C-x"`, it is a String since ruby 1.9.

Author: nobu

test/io/console/test_io_console.rb

@@ -373,10 +373,10 @@ def assert_ctrl(expect, cc, r, w)
     w.flush
     result = EnvUtil.timeout(3) {r.gets}
     if result
-      case cc
-      when 0..31
+      case cc.chr
+      when "\C-A".."\C-_"
         cc = "^" + (cc.ord | 0x40).chr
-      when 127
+      when "\C-?"
         cc = "^?"
       end
       result.sub!(cc, "")