tool_paramhlp: Fixed display of URL index in password prompt for --next

Commit f3bae6e added the URL index to the password prompt when using
--next. Unfortunately, because the size_t specifier (%zu) is not
supported by all sprintf() implementations we use the curl_off_t format
specifier instead. The display of an incorrect value arises on platforms
where size_t and curl_off_t are of a different size.

src/tool_paramhlp.c

@@ -426,7 +426,7 @@ static CURLcode checkpasswd(const char *kind, /* for what purpose */
       curlx_msnprintf(prompt, sizeof(prompt),
                       "Enter %s password for user '%s' on URL #%"
                       CURL_FORMAT_CURL_OFF_TU ":",
-                      kind, *userpwd, i + 1);
+                      kind, *userpwd, (curl_off_t) (i + 1));
 
     /* get password */
     getpass_r(prompt, passwd, sizeof(passwd));