detect_charset (WWW::Mechanize::Util)

    # File lib/www/mechanize/util.rb, line 60
            def detect_charset(src)
              tmp = NKF.guess(src || "<html></html>")
              if RUBY_VERSION >= "1.9.0"
                enc = tmp.to_s.upcase
              else
                enc = NKF.constants.find{|c|
                  NKF.const_get(c) == tmp
                }
                enc = CODE_DIC[enc.intern]
              end
              enc || "ISO-8859-1"
            end