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

tests/libtest/lib1535.c

@@ -80,7 +80,7 @@ static CURLcode test_lib1535(const char *URL)
   if(protocol != CURLPROTO_HTTP) {
     curl_mfprintf(stderr,
                   "%s:%d protocol of http resource is incorrect; "
-                  "expected %d but is %ld\n",
+                  "expected %ld but is %ld\n",
                   __FILE__, __LINE__, CURLPROTO_HTTP, protocol);
     res = CURLE_HTTP_RETURNED_ERROR;
     goto test_cleanup;