CURLOPT: bump CURLFTP* enums to long, drop casts

This patch bumps the size of these constants 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:

- CURLFTP_CREATE_DIR
- CURLFTP_CREATE_DIR_NONE
- CURLFTP_CREATE_DIR_RETRY
- CURLFTPAUTH_DEFAULT
- CURLFTPAUTH_SSL
- CURLFTPAUTH_TLS
- CURLFTPMETHOD_DEFAULT
- CURLFTPMETHOD_MULTICWD
- CURLFTPMETHOD_NOCWD
- CURLFTPMETHOD_SINGLECWD
- CURLFTPSSL_CCC_ACTIVE
- CURLFTPSSL_CCC_NONE
- CURLFTPSSL_CCC_PASSIVE

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

Closes #17797

src/config2setopts.c

@@ -653,7 +653,7 @@ static CURLcode ftp_setopts(struct OperationConfig *config, CURL *curl)
 
   /* new in curl 7.16.1 */
   if(config->ftp_ssl_ccc)
-    my_setopt_enum(curl, CURLOPT_FTP_SSL_CCC, (long)config->ftp_ssl_ccc_mode);
+    my_setopt_enum(curl, CURLOPT_FTP_SSL_CCC, config->ftp_ssl_ccc_mode);
 
   my_setopt_str(curl, CURLOPT_FTP_ACCOUNT, config->ftp_account);
 

src/tool_cfgable.h

@@ -226,8 +226,8 @@ struct OperationConfig {
   unsigned long timecond;
   HttpReq httpreq;
   long proxyver;             /* set to CURLPROXY_HTTP* define */
-  int ftp_ssl_ccc_mode;
-  int ftp_filemethod;
+  long ftp_ssl_ccc_mode;
+  long ftp_filemethod;
   enum {
     CLOBBER_DEFAULT, /* Provides compatibility with previous versions of curl,
                         by using the default behavior for -o, -O, and -J.

src/tool_paramhlp.c

@@ -620,7 +620,7 @@ ParameterError add2list(struct curl_slist **list, const char *ptr)
   return PARAM_OK;
 }
 
-int ftpfilemethod(struct OperationConfig *config, const char *str)
+long ftpfilemethod(struct OperationConfig *config, const char *str)
 {
   if(curl_strequal("singlecwd", str))
     return CURLFTPMETHOD_SINGLECWD;
@@ -635,7 +635,7 @@ int ftpfilemethod(struct OperationConfig *config, const char *str)
   return CURLFTPMETHOD_MULTICWD;
 }
 
-int ftpcccmethod(struct OperationConfig *config, const char *str)
+long ftpcccmethod(struct OperationConfig *config, const char *str)
 {
   if(curl_strequal("passive", str))
     return CURLFTPSSL_CCC_PASSIVE;

src/tool_paramhlp.h

@@ -58,9 +58,9 @@ CURLcode get_args(struct OperationConfig *config, const size_t i);
 
 ParameterError add2list(struct curl_slist **list, const char *ptr);
 
-int ftpfilemethod(struct OperationConfig *config, const char *str);
+long ftpfilemethod(struct OperationConfig *config, const char *str);
 
-int ftpcccmethod(struct OperationConfig *config, const char *str);
+long ftpcccmethod(struct OperationConfig *config, const char *str);
 
 long delegation(struct OperationConfig *config, const char *str);