Update networking layer w/ CURL and emscripten impl

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

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+---
+c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+SPDX-License-Identifier: curl
+Title: curl_global_init_mem
+Section: 3
+Source: libcurl
+See-also:
+  - curl_global_cleanup (3)
+  - curl_global_init (3)
+Protocol:
+  - All
+Added-in: 7.12.0
+---
+
+# NAME
+
+curl_global_init_mem - global libcurl initialization with memory callbacks
+
+# SYNOPSIS
+
+~~~c
+#include <curl/curl.h>
+
+CURLcode curl_global_init_mem(long flags,
+                              curl_malloc_callback m,
+                              curl_free_callback f,
+                              curl_realloc_callback r,
+                              curl_strdup_callback s,
+                              curl_calloc_callback c);
+~~~
+
+# DESCRIPTION
+
+This function works exactly as curl_global_init(3) with one addition: it
+allows the application to set callbacks to replace the otherwise used internal
+memory functions.
+
+If you are using libcurl from multiple threads or libcurl was built with the
+threaded resolver option then the callback functions must be thread safe. The
+threaded resolver is a common build option to enable (and in some cases the
+default) so we strongly urge you to make your callback functions thread safe.
+
+All callback arguments must be set to valid function pointers. The
+prototypes for the given callbacks must match these:
+
+## `void *malloc_callback(size_t size);`
+
+To replace malloc()
+
+## `void free_callback(void *ptr);`
+
+To replace free()
+
+## `void *realloc_callback(void *ptr, size_t size);`
+
+To replace realloc()
+
+## `char *strdup_callback(const char *str);`
+
+To replace strdup()
+
+## `void *calloc_callback(size_t nmemb, size_t size);`
+
+To replace calloc()
+
+This function is otherwise the same as curl_global_init(3), please refer
+to that man page for documentation.
+
+# CAUTION
+
+Manipulating these gives considerable powers to the application to severely
+screw things up for libcurl. Take care.
+
+# %PROTOCOLS%
+
+# EXAMPLE
+
+~~~c
+extern void *malloc_cb(size_t);
+extern void free_cb(void *);
+extern void *realloc_cb(void *, size_t);
+extern char *strdup_cb(const char *);
+extern void *calloc_cb(size_t, size_t);
+
+int main(void)
+{
+  curl_global_init_mem(CURL_GLOBAL_DEFAULT, malloc_cb,
+                       free_cb, realloc_cb,
+                       strdup_cb, calloc_cb);
+}
+~~~
+
+# %AVAILABILITY%
+
+# RETURN VALUE
+
+This function returns a CURLcode indicating success or error.
+
+CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
+libcurl-errors(3). If CURLOPT_ERRORBUFFER(3) was set with curl_easy_setopt(3)
+there can be an error message stored in the error buffer when non-zero is
+returned.