Multiple Set-Cookie headers in CPPRESTSDK

Hi,

I found that the implementation of web::http::http_header::add simply append the old header value with a new value using comma(',') as a separator.

    void add(const key_type& name, const _t1& value)
    {
        if (has(name))
        {
            m_headers[name] =  m_headers[name].append(_XPLATSTR(", ") + utility::conversions::print_string(value));
        }
        else
        {
            m_headers[name] = utility::conversions::print_string(value);
        }
    }

This make all "Set-Cookie" headers combined into one. It breaks the rfc6265 and it does not work for all browsers(i tested with Chrome, IE, and FireFox).

here is a snapshot for the RFC

Origin servers SHOULD NOT fold multiple Set-Cookie header fields into
   a single header field.  The usual mechanism for folding HTTP headers
   fields (i.e., as defined in [RFC2616]) might change the semantics of
   the Set-Cookie header field because the %x2C (",") character is used
   by Set-Cookie in a way that conflicts with such folding.

What I expect is that everytimes I call web::http::http_header::add I should get multiple 'Set-Header' in response.

So please advise if this should be fixed in the library.