Adds asio library and Storage Module

lib/asio-1.18.0/doc/asio/overview/posix/fork.html

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+<div class="titlepage"><div><div><h4 class="title">
+<a name="asio.overview.posix.fork"></a><a class="link" href="fork.html" title="Fork">Fork</a>
+</h4></div></div></div>
+<p>
+          Asio supports programs that utilise the <code class="computeroutput">fork()</code> system call.
+          Provided the program calls <code class="computeroutput">io_context.notify_fork()</code> at the
+          appropriate times, Asio will recreate any internal file descriptors (such
+          as the "self-pipe trick" descriptor used for waking up a reactor).
+          The notification is usually performed as follows:
+        </p>
+<pre class="programlisting">io_context_.notify_fork(asio::io_context::fork_prepare);
+if (fork() == 0)
+{
+  io_context_.notify_fork(asio::io_context::fork_child);
+  ...
+}
+else
+{
+  io_context_.notify_fork(asio::io_context::fork_parent);
+  ...
+}
+</pre>
+<p>
+          User-defined services can also be made fork-aware by overriding the <code class="computeroutput">io_context::service::notify_fork()</code>
+          virtual function.
+        </p>
+<p>
+          Note that any file descriptors accessible via Asio's public API (e.g. the
+          descriptors underlying <code class="computeroutput">basic_socket&lt;&gt;</code>, <code class="computeroutput">posix::stream_descriptor</code>,
+          etc.) are not altered during a fork. It is the program's responsibility
+          to manage these as required.
+        </p>
+<h6>
+<a name="asio.overview.posix.fork.h0"></a>
+          <span><a name="asio.overview.posix.fork.see_also"></a></span><a class="link" href="fork.html#asio.overview.posix.fork.see_also">See
+          Also</a>
+        </h6>
+<p>
+          <a class="link" href="../../reference/io_context/notify_fork.html" title="io_context::notify_fork">io_context::notify_fork()</a>,
+          <a class="link" href="../../reference/io_context/fork_event.html" title="io_context::fork_event">io_context::fork_event</a>,
+          <a class="link" href="../../reference/execution_context__service/notify_fork.html" title="execution_context::service::notify_fork">io_context::service::notify_fork()</a>,
+          <a class="link" href="../../examples/cpp03_examples.html#asio.examples.cpp03_examples.fork">Fork examples</a>.
+        </p>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M.
+      Kohlhoff<p>
+        Distributed under the Boost Software License, Version 1.0. (See accompanying
+        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+      </p>
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