url: Fixed connection re-use when using different log-in credentials

In addition to FTP, other connection based protocols such as IMAP, POP3,
SMTP, SCP, SFTP and LDAP require a new connection when different log-in
credentials are specified. Fixed the detection logic to include these
other protocols.

Bug: http://curl.haxx.se/docs/adv_20140326A.html

lib/http.c

@@ -145,7 +145,7 @@ const struct Curl_handler Curl_handler_https = {
   ZERO_NULL,                            /* readwrite */
   PORT_HTTPS,                           /* defport */
   CURLPROTO_HTTP | CURLPROTO_HTTPS,     /* protocol */
-  PROTOPT_SSL                           /* flags */
+  PROTOPT_SSL | PROTOPT_CREDSPERREQUEST /* flags */
 };
 #endif