title: Convert mpz_t to binary representation
body: <p>I'm using mpz_t for big numbers. I need to convert the mpz_t to binary representation. I tried to use the mpz_export, but the returned array contains only 0s.</p>
  
  <pre><code>mpz_t test;
  mpz_init(test);
  string myString = "173065661579367924163593258659639227443747684437943794002725938880375168921999825584315046";
      mpz_set_str(test,myString.c_str(),10);
      int size = mpz_sizeinbase(test,2);
      cout &lt;&lt; "size is : "&lt;&lt; size&lt;&lt;endl;
      byte *rop = new byte[size];
      mpz_export(rop,NULL,1,sizeof(rop),1,0,test);
  </code></pre>