Use slirp_pollfds_fill_socket on libslirp >= 4.9.0

slirp_pollfds_fill and its int-based SlirpAddPollCb callback were
deprecated in libslirp 4.9.0 in favour of slirp_pollfds_fill_socket and
SlirpAddPollSocketCb, which carry the descriptor as a slirp_os_socket.
Building against libslirp >= 4.9.0 therefore emits a
-Wdeprecated-declarations warning in vReceiveThread.

Guard the poll-fill call and the add-poll callback signature on
SLIRP_CHECK_VERSION( 4, 9, 0 ) so modern libslirp uses the socket-based
API while older versions keep the existing behaviour.

Fixes #1325

Author: archigup

source/portable/NetworkInterface/libslirp/MBuffNetifBackendLibslirp.c

@@ -575,14 +575,21 @@ static inline int lNativePollEventsToSlirpEvents( int lPosixPollFlags )
 }
 
 /**
- * @brief SlirpAddPollCb implementation passed to libslirp during initialization.
- * @param [in] fd File descriptor to add to the polling list.
+ * @brief SlirpAddPollCb / SlirpAddPollSocketCb implementation passed to libslirp
+ * during initialization.
+ * @param [in] lFd File descriptor to add to the polling list.
  * @param [in] lSlirpFlags Flags to be placed in the relevant events field.
  * @param [in] pvOpaque Opaque pointer to the relevant SlirpBackendContext_t.
  */
-static int lSlirpAddPollCallback( int lFd,
-                                  int lSlirpFlags,
-                                  void * pvOpaque )
+#if SLIRP_CHECK_VERSION( 4U, 9U, 0U )
+    static int lSlirpAddPollCallback( slirp_os_socket lFd,
+                                      int lSlirpFlags,
+                                      void * pvOpaque )
+#else
+    static int lSlirpAddPollCallback( int lFd,
+                                      int lSlirpFlags,
+                                      void * pvOpaque )
+#endif
 {
     SlirpBackendContext_t * pxCtx = ( SlirpBackendContext_t * ) pvOpaque;
 
@@ -706,7 +713,11 @@ static THREAD_RETURN THREAD_FUNC_DEF vReceiveThread( void * pvParameters )
         vLockSlirpContext( pxCtx );
         {
             pxCtx->nfds = 0;
-            slirp_pollfds_fill( pxCtx->pxSlirp, &ulPollerTimeoutMs, lSlirpAddPollCallback, pxCtx );
+            #if SLIRP_CHECK_VERSION( 4U, 9U, 0U )
+                slirp_pollfds_fill_socket( pxCtx->pxSlirp, &ulPollerTimeoutMs, lSlirpAddPollCallback, pxCtx );
+            #else
+                slirp_pollfds_fill( pxCtx->pxSlirp, &ulPollerTimeoutMs, lSlirpAddPollCallback, pxCtx );
+            #endif
         }
         vUnlockSlirpContext( pxCtx );