lib: connection filters (cfilter) addition to curl:

- general construct/destroy in connectdata
 - default implementations of callback functions
 - connect: cfilters for connect and accept
 - socks: cfilter for socks proxying
 - http_proxy: cfilter for http proxy tunneling
 - vtls: cfilters for primary and proxy ssl
 - change in general handling of data/conn
 - Curl_cfilter_setup() sets up filter chain based on data settings,
   if none are installed by the protocol handler setup
 - Curl_cfilter_connect() boot straps filters into `connected` status,
   used by handlers and multi to reach further stages
 - Curl_cfilter_is_connected() to check if a conn is connected,
   e.g. all filters have done their work
 - Curl_cfilter_get_select_socks() gets the sockets and READ/WRITE
   indicators for multi select to work
 - Curl_cfilter_data_pending() asks filters if the have incoming
   data pending for recv
 - Curl_cfilter_recv()/Curl_cfilter_send are the general callbacks
   installed in conn->recv/conn->send for io handling
 - Curl_cfilter_attach_data()/Curl_cfilter_detach_data() inform filters
   and addition/removal of a `data` from their connection
 - adding vtl functions to prevent use of Curl_ssl globals directly
   in other parts of the code.

Reviewed-by: Daniel Stenberg
Closes #9855

lib/smb.c

@@ -38,6 +38,7 @@
 #include "urldata.h"
 #include "sendf.h"
 #include "multiif.h"
+#include "cfilters.h"
 #include "connect.h"
 #include "progress.h"
 #include "transfer.h"
@@ -666,8 +667,8 @@ static CURLcode smb_connection_state(struct Curl_easy *data, bool *done)
 #ifdef USE_SSL
     if((conn->handler->flags & PROTOPT_SSL)) {
       bool ssl_done = FALSE;
-      result = Curl_ssl_connect_nonblocking(data, conn, FALSE,
-                                            FIRSTSOCKET, &ssl_done);
+      result = Curl_cfilter_connect(data, conn, FIRSTSOCKET,
+                                    FALSE, &ssl_done);
       if(result && result != CURLE_AGAIN)
         return result;
       if(!ssl_done)