CURLOPT: bump `CURL_REDIR_*` macros to `long`

CURLOPT: bump `CURL_REDIR_*` macros to `long`

This patch bumps the size of these macros from `int` to `long`, while
keeping their actual values the same. It may cause incompatibilities in
user code, requiring the bump of holder variables and/or adding casts:

- CURL_REDIR_GET_ALL
- CURL_REDIR_POST_301
- CURL_REDIR_POST_302
- CURL_REDIR_POST_303
- CURL_REDIR_POST_ALL

Also:
- keep existing cast within the documentation to make sure it applies
  to older curl versions as well.

Closes #18110