CURLOPT: bump remaining 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:

- CURLGSSAPI_DELEGATION_FLAG
- CURLGSSAPI_DELEGATION_NONE
- CURLGSSAPI_DELEGATION_POLICY_FLAG

- CURLMIMEOPT_FORMESCAPE

- CURLSSH_AUTH_AGENT
- CURLSSH_AUTH_ANY
- CURLSSH_AUTH_DEFAULT
- CURLSSH_AUTH_GSSAPI
- CURLSSH_AUTH_HOST
- CURLSSH_AUTH_KEYBOARD
- CURLSSH_AUTH_NONE
- CURLSSH_AUTH_PASSWORD
- CURLSSH_AUTH_PUBLICKEY

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

Closes #18134

docs/examples/sftpget.c

@@ -86,7 +86,7 @@ int main(void)
     /* We activate ssh agent. For this to work you need
        to have ssh-agent running (type set | grep SSH_AGENT to check) or
        pageant on Windows (there is an icon in systray if so) */
-    curl_easy_setopt(curl, CURLOPT_SSH_AUTH_TYPES, (long)CURLSSH_AUTH_AGENT);
+    curl_easy_setopt(curl, CURLOPT_SSH_AUTH_TYPES, CURLSSH_AUTH_AGENT);
 #endif
 
     /* Switch on full protocol/debug output */