title: What are the valid alignment values for std::align_val_t for C++ allocators?
body: <p>Now that C++ has several additional new and delete operators with std::align_val_t parameters, what are the valid values for them?</p>
  
  <p>Are they 1, 2, 4, 8, ... and so forth?</p>
  
  <p>Is there an upper limit to the values?</p>
  
  <p>Defined by the compiler?</p>