title: incrementing value of column value with updateAll()
body: <p>This works very well:</p>
  
  <pre><code>   $test = self::updateAll(
                          array( 'left_nr' =&gt; '3',
                                 'right_nr' =&gt; '3', ),
                          'left_nr&gt;=:left_nr AND right_nr&gt;=:right_nr',
                          array(
                              ':left_nr' =&gt; $parent-&gt;left_nr,
                              ':right_nr' =&gt; $parent-&gt;right_nr,
                              //':new_left_nr' =&gt; 'left_nr + 2',
                              //':new_right_nr' =&gt; 'right_nr + 2'
  
                          )
                      );
  </code></pre>
  
  <p>but what I want is:</p>
  
  <pre><code>   $test = self::updateAll(
                          array( 'left_nr' =&gt; ':new_left_nr',
                                 'right_nr' =&gt; ':new_right_nr', ),
                          'left_nr&gt;=:left_nr AND right_nr&gt;=:right_nr',
                          array(
                              ':left_nr' =&gt; $parent-&gt;left_nr,
                              ':right_nr' =&gt; $parent-&gt;right_nr,
                              ':new_left_nr' =&gt; 'left_nr + 2',
                             ':new_right_nr' =&gt; 'right_nr + 2'
  
                          )
                      );
  </code></pre>
  
  <p>When I try that code, I get following error:</p>
  
  <p>CDbCommand failed to execute the SQL statement: SQLSTATE[HY093]: Invalid parameter number: number of bound variables does not match number of tokens. The SQL statement executed was: UPDATE <code>test_nested_set</code> SET <code>left_nr</code>=:yp0, <code>right_nr</code>=:yp1 WHERE left_nr>=:left_nr AND right_nr>=:right_nr</p>
  
  <p>How can I achieve it?</p>