[PHP 8.4] Curl: Add CURLOPT_TCP_KEEPCNT option

Commit: php/php-src#15446
PHP.Watch: [PHP 8.4: Curl: New `CURLOPT_TCP_KEEPCNT` option](https://php.watch/versions/8.4/CURLOPT_TCP_KEEPCNT)

reference/curl/constants_curl_setopt.xml

@@ -3855,6 +3855,8 @@
      frequency of these probes can be controlled by the <constant>CURLOPT_TCP_KEEPIDLE</constant>
      and <constant>CURLOPT_TCP_KEEPINTVL</constant> options, provided the operating system
      supports them. If set to <literal>0</literal> (default) keepalive probes are disabled.
+     The maximum number of probes can be set with the <constant>CURLOPT_TCP_KEEPCNT</constant>
+     option.
      Available as of cURL 7.25.0.
     </para>
    </listitem>
@@ -3889,6 +3891,19 @@
     </para>
    </listitem>
   </varlistentry>
+  <varlistentry xml:id="constant.curlopt-tcp-keepcnt">
+   <term>
+    <constant>CURLOPT_TCP_KEEPCNT</constant>
+    (<type>int</type>)
+   </term>
+   <listitem>
+    <para>
+     Sets the maximum number of TCP keep-alive probes.
+     The default is <literal>9</literal>.
+     Available as of PHP 8.4.0 and cURL 8.9.0.
+    </para>
+   </listitem>
+  </varlistentry>
   <varlistentry xml:id="constant.curlopt-tcp-nodelay">
    <term>
     <constant>CURLOPT_TCP_NODELAY</constant>