tool_cb_hdr: allow etag and content-disposition for 3xx reply

- Parse etag and content-disposition headers for 3xx replies.

For example, a server may send a content-disposition filename header
with a redirect reply (3xx) but not with the final response (2xx).
Without this change curl would ignore the server's specified filename
and continue to use the filename extracted from the user-specified URL.

Prior to this change, 75d79a4 had limited etag and content-disposition
to 2xx replies only.

Tests-by: Daniel Stenberg

Reported-by: Morgan Willcock
Fixes https://github.com/curl/curl/issues/13302
Closes #13484

src/tool_cb_hdr.c

@@ -118,8 +118,9 @@ size_t tool_header_cb(char *ptr, size_t size, size_t nmemb, void *userdata)
     long response = 0;
     curl_easy_getinfo(per->curl, CURLINFO_RESPONSE_CODE, &response);
 
-    if(response/100 != 2)
-      /* only care about these headers in 2xx responses */
+    if((response/100 != 2) && (response/100 != 3))
+      /* only care about etag and content-disposition headers in 2xx and 3xx
+         responses */
       ;
     /*
      * Write etag to file when --etag-save option is given.