title: Convert uint64_t to std::string
body: <p>How can I transfer uint64_t value to std::string?
  I need to construct the std::string containing this value
  For example something like this:</p>
  
  <pre><code>void genString(uint64_t val)
  {
        std::string str;
        //.....some code for str 
        str+=(unsigned int)val;//????
  }
  </code></pre>
  
  <p>Thank you</p>