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

CURLOPT: bump `CURLPROTO_*` 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:

- CURLPROTO_HTTP
- CURLPROTO_HTTPS
- CURLPROTO_FTP
- CURLPROTO_FTPS
- CURLPROTO_SCP
- CURLPROTO_SFTP
- CURLPROTO_TELNET
- CURLPROTO_LDAP
- CURLPROTO_LDAPS
- CURLPROTO_DICT
- CURLPROTO_FILE
- CURLPROTO_TFTP
- CURLPROTO_IMAP
- CURLPROTO_IMAPS
- CURLPROTO_POP3
- CURLPROTO_POP3S
- CURLPROTO_SMTP
- CURLPROTO_SMTPS
- CURLPROTO_RTSP
- CURLPROTO_RTMP
- CURLPROTO_RTMPT
- CURLPROTO_RTMPE
- CURLPROTO_RTMPTE
- CURLPROTO_RTMPS
- CURLPROTO_RTMPTS
- CURLPROTO_GOPHER
- CURLPROTO_SMB
- CURLPROTO_SMBS
- CURLPROTO_MQTT
- CURLPROTO_GOPHERS
- CURLPROTO_ALL

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

Closes #18136