title: dplyr Create new boolean variable from any_vars() filter condition
body: <p>I would like to create a boolean variable based on a condition of multiple variables. As shown in the second answer to <a href="https://stackoverflow.com/questions/28233561/finding-rows-containing-a-value-or-values-in-any-column">this question</a>, one can filter based on many conditions across a number of columns:</p>
  
  <pre class="lang-r prettyprint-override"><code> mtcars %&gt;% filter_at(vars(starts_with("d"),starts_with("c")), any_vars(. %in% c(4)))
  </code></pre>
  
  <p>I would like to do something like</p>
  
  <pre class="lang-r prettyprint-override"><code>test &lt;- mtcars %&gt;% mutate(has.4 = any_vars(vars(starts_with("d"),starts_with("c")) %in% c(4)))
  </code></pre>
  
  <p>but this of course does not work and gives <code>Error: Column ``has.4`` is of unsupported type quoted call</code>.</p>
  
  <p>The <code>filter_at()</code> call is already creating the boolean with which to subset the data on. How can I pipe that output into a new variable, and keep all rows?</p>
  
  <p>Also, I only want to create one new column, so <code>mutate_at()</code> and <code>mutate_if()</code> don't seem to be the right calls.</p>