title: cbind with duplicated row names in one of the tables
body: <p>I am trying to merge two data sets by columns:</p>
  
  <pre><code>&gt; x
     ID XD
  1 sll0001 A
  2 sll0002 B
  3 sll0003 C
  
  &gt; y
     ID      XD
  1 sll0001 go_0002
  2 sll0001 go_0003
  3 sll0003 go_0003
  4 sll0003 go_0004
  5 sll0004 go_0005
  </code></pre>
  
  <p>And I would like to get something like this:</p>
  
  <pre><code>&gt; xy
     ID   XD    XD.1    XD.2
  1 sll0001    A go_0002 go_0003
  2 sll0002    B    &lt;NA&gt;    &lt;NA&gt;
  3 sll0003    C go_0004    &lt;NA&gt;
  4 sll0004 &lt;NA&gt; go_0005    &lt;NA&gt;
  </code></pre>
  
  <p>My problem is that cbind() does not permit to use duplicated row names. Any idea? thanks!</p>