cookies: first n/v pair in Set-Cookie: is the cookie, then parameters

RFC 6265 section 4.1.1 spells out that the first name/value pair in the
header is the actual cookie name and content, while the following are
the parameters.

libcurl previously had a more liberal approach which causes significant
problems when introducing new cookie parameters, like the suggested new
cookie priority draft.

The previous logic read all n/v pairs from left-to-right and the first
name used that wassn't a known parameter name would be used as the
cookie name, thus accepting "Set-Cookie: Max-Age=2; person=daniel" to be
a cookie named 'person' while an RFC 6265 compliant parser should
consider that to be a cookie named 'Max-Age' with an (unknown) parameter
'person'.

Fixes #709

tests/data/test1218

@@ -14,7 +14,7 @@ cookies
 <data>
 HTTP/1.1 200 OK
 Date: Tue, 25 Sep 2001 19:37:44 GMT
-Set-Cookie: domain=.example.fake; bug=fixed;
+Set-Cookie: bug=fixed; domain=.example.fake;
 Content-Length: 21
 
 This server says moo

tests/data/test27

@@ -11,7 +11,7 @@ cookies
 <data>
 HTTP/1.1 200 Mooo swsclose
 Connection: close
-Set-Cookie: path=/; thewinneris=nowayyouwin;
+Set-Cookie: thewinneris=nowayyouwin; path=/;
 Content-Length: 8
 
 *flopp*