title: a variadic template as a template parameter without pack expansion
body: <p>I found that the following code compiles and runs successfully with VS 2015:</p>
  
  <pre><code>template&lt;typename T, template &lt;typename ...&gt; class Container &gt;
  struct Holder
  {
      Container&lt;T&gt; container_;
  };
  
  int main()
  {
      Holder&lt;int, std::vector&gt; h;
      h.container_.push_back(10);
      std::cout &lt;&lt; h.container_.at(0);
  }
  </code></pre>
  
  <p>Could you please tell me whether this way follows the standard to specify a template-template parameter without listing parameter types (type of the container elements and allocator type in the above example)?</p>