title: Set last `n` bits in unsigned int
body: <p>How to set (in most elegant way) exactly <code>n</code> least significant bits of <code>uint32_t</code>? That is to write a function <code>void setbits(uint32_t *x, int n);</code>. Function should handle each <code>n</code> from <code>0</code> to <code>32</code>.</p>
  
  <p>Especially value <code>n==32</code> should be handled.</p>