title: iphone x: keep search bar within safe zone
body: <p>Upgrading our application to support iPhone X.  How can I add a search bar to the header of a table view and have it within the safe zone?  Here is how we currently build the search bar.    </p>
  
  <pre><code>let searchController = UISearchController(searchResultsController: nil)
  func buildSearchBar() {
      self.searchController.searchResultsUpdater = self
      self.searchController.hidesNavigationBarDuringPresentation = false
      self.searchController.dimsBackgroundDuringPresentation = false
      self.searchController.searchBar.sizeToFit()
      self.tableView.tableHeaderView = searchController.searchBar
  
      self.definesPresentationContext = true
  }
  </code></pre>