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

CURLOPT: bump `CURL_SSLVERSION_*` 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_SSLVERSION_DEFAULT
- CURL_SSLVERSION_SSLv2
- CURL_SSLVERSION_SSLv3
- CURL_SSLVERSION_TLSv1
- CURL_SSLVERSION_TLSv1_0
- CURL_SSLVERSION_TLSv1_1
- CURL_SSLVERSION_TLSv1_2
- CURL_SSLVERSION_TLSv1_3

- CURL_SSLVERSION_MAX_DEFAULT
- CURL_SSLVERSION_MAX_NONE
- CURL_SSLVERSION_MAX_TLSv1_0
- CURL_SSLVERSION_MAX_TLSv1_1
- CURL_SSLVERSION_MAX_TLSv1_2
- CURL_SSLVERSION_MAX_TLSv1_3

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

Closes #18135