title: big ints with boost : too large to be represented in any integer type
body: <p>I think i don't get something.</p>
  <p>Is the class <code>cpp_int</code> from <code>boost::multiprecision</code> supposed to hold integers as big as one want ?
  Let's say i want to store the following ridiculously big integer. How am I supposed to do it ?</p>
  <pre><code>#include &lt;boost/multiprecision/cpp_int.hpp&gt;
  
  using namespace boost::multiprecision;
  
  cpp_int n = 999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999;
  </code></pre>
  <p>The following code returns</p>
  <p><code> error: integer literal is too large to be represented in any integer type</code></p>