Update networking layer w/ CURL and emscripten impl

External/curl-8.17.0/docs/libcurl/curl_multi_cleanup.md

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+---
+c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+SPDX-License-Identifier: curl
+Title: curl_multi_cleanup
+Section: 3
+Source: libcurl
+See-also:
+  - curl_easy_cleanup (3)
+  - curl_easy_init (3)
+  - curl_multi_get_handles (3)
+  - curl_multi_init (3)
+Protocol:
+  - All
+Added-in: 7.9.6
+---
+
+# NAME
+
+curl_multi_cleanup - close down a multi session
+
+# SYNOPSIS
+
+~~~c
+#include <curl/curl.h>
+
+CURLMcode curl_multi_cleanup(CURLM *multi_handle);
+~~~
+
+# DESCRIPTION
+
+This function is the opposite of curl_multi_init(3). Cleans up and removes a
+whole multi stack. It does not free or touch any individual easy handles in
+any way - they still need to be closed individually, using the usual
+curl_easy_cleanup(3) way. The order of cleaning up should be:
+
+1 - curl_multi_remove_handle(3) before any easy handles are cleaned up
+
+2 - curl_easy_cleanup(3) can now be called independently since the easy
+handle is no longer connected to the multi handle
+
+3 - curl_multi_cleanup(3) should be called when all easy handles are
+removed
+
+When this function is called, remaining entries in the connection pool held by
+the multi handle are shut down, which might trigger calls to the
+CURLMOPT_SOCKETFUNCTION(3) callback.
+
+Passing in a NULL pointer in *multi_handle* makes this function return
+CURLM_BAD_HANDLE immediately with no other action.
+
+Any use of the **multi_handle** after this function has been called and have
+returned, is illegal.
+# %PROTOCOLS%
+
+# EXAMPLE
+
+~~~c
+int main(void)
+{
+  CURLM *multi = curl_multi_init();
+
+  /* when the multi transfer is done ... */
+
+  /* remove all easy handles, then: */
+  curl_multi_cleanup(multi);
+}
+~~~
+
+# %AVAILABILITY%
+
+# RETURN VALUE
+
+This function returns a CURLMcode indicating success or error.
+
+CURLM_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3).