[httpclient] bug in HttpClient.parseHeaders()

[Vincent Massol]

The parseHeaders() does not support multiple headers with the same name (it
is using an hashtable). However, according to the spec. it is allowed to
have several "set-cookie" headers :

RFC 2109, Page 3, " An origin server may include multiple Set-Cookie headers
in a response.  Note that an intervening gateway could fold multiple such
headers into a single header."

Thanks
-Vincent