Bug 629710 - escape_string does not check '\<HEX><HEX>'
    
    https://bugzilla.redhat.com/show_bug.cgi?id=629710
    Resolves: 629710
    Description: do_escape_string (core of escape_string) converts
    '\\ (backslash)' to '\5C' even if the following 2 characters are
    hex digits.  That is, the character is already escaped.  This
    patch checks the case and if it is, it does not escape it further.