--- strip
--- strip!

    ƬζʸƼޤ
    ʸ " \t\r\n\f\v" Ǥ

    strip ѹʸ򿷤֤ޤ

    strip!  self ѹ֤ޤ
    򤬤ʤäȤ nil ֤ޤ

        p "  abc  \r\n".strip    #=> "abc"
        p "abc\n".strip          #=> "abc"
        p "  abc".strip          #=> "abc"
        p "abc".strip            #=> "abc"

        str = "\tabc\n"
        p str.strip              #=> "abc"
        p str                    #=> "\tabc\n"  (Ѳʤ)

        str = "  abc\r\n"
        p str.strip!             #=> "abc"
        p str                    #=> "abc"  (Ѳ)

        str = "abc"
        p str.strip!             #=> nil
        p str                    #=> "abc"

