websocket: add option to disable auto-pong reply

This adds another bitflag on CURLOPT_WS_OPTIONS (CURLWS_NOAUTOPONG) that
disables the default and automatic PONG reply in the WebSocket layer.

Assisted-by: Calvin Ruocco

Closes #16744

docs/internals/WEBSOCKET.md

@@ -39,7 +39,8 @@ WebSocket with libcurl can be done two ways.
 The new options to `curl_easy_setopt()`:
 
  `CURLOPT_WS_OPTIONS` - to control specific behavior. `CURLWS_RAW_MODE` makes
- libcurl provide all WebSocket traffic raw in the callback.
+ libcurl provide all WebSocket traffic raw in the callback. `CURLWS_NOAUTOPONG`
+ disables automatic `PONG` replies.
 
 The new function calls:
 

docs/libcurl/curl_ws_meta.md

@@ -106,7 +106,8 @@ This is a ping message. It may contain up to 125 bytes of payload text.
 libcurl does not verify that the payload is valid UTF-8.
 
 Upon receiving a ping message, libcurl automatically responds with a pong
-message unless the **CURLWS_RAW_MODE** bit of CURLOPT_WS_OPTIONS(3) is set.
+message unless the **CURLWS_NOAUTOPONG** or **CURLWS_RAW_MODE** bit of
+CURLOPT_WS_OPTIONS(3) is set.
 
 ## CURLWS_PONG
 

docs/libcurl/libcurl-ws.md

@@ -88,7 +88,8 @@ unidirectional heartbeat.
 
 libcurl automatically responds to server PING messages with a PONG that echoes
 the payload of the PING message. libcurl does neither send any PING messages
-nor any unsolicited PONG messages automatically.
+nor any unsolicited PONG messages automatically. The automatic reply to PING
+messages can be disabled through CURLOPT_WS_OPTIONS(3).
 
 # MODELS
 

docs/libcurl/opts/CURLOPT_WS_OPTIONS.md

@@ -44,6 +44,12 @@ callback.
 In raw mode, libcurl does not handle pings or any other frame for the
 application.
 
+## CURLWS_NOAUTOPONG (2)
+
+Disable the automatic reply to PING messages. This means users must
+send a PONG message with curl_ws_send(3). This feature is added with
+version 8.14.0.
+
 # DEFAULT
 
 0

docs/libcurl/symbols-in-versions

@@ -1155,6 +1155,7 @@ CURLWARNING                     7.66.0
 CURLWS_BINARY                   7.86.0
 CURLWS_CLOSE                    7.86.0
 CURLWS_CONT                     7.86.0
+CURLWS_NOAUTOPONG               8.14.0
 CURLWS_OFFSET                   7.86.0
 CURLWS_PING                     7.86.0
 CURLWS_PONG                     7.86.0