title: Custom UITableViewCell refreshes constraints from xib file when rotating
body: <p>So i subclassed UITableViewCell and have an appropriate xib file for it.<br>
  To keep it simple lets just say i have 3 <code>UILabel</code>s side by side.<br>
  All of them have a spacing of 8 to each other and are resized to fit its content except the first one, which takes the remaining space in the cell.<br>
  The first label (Label1) has trailing space constraints to both other labels and the superview. Those constraints have their <code>Installed</code> property not checked and are connected to my subclass via <code>IBOutlet</code>s.<br>
  Visually it could look like this:<br></p>
  
  <p>[Label1] - Spacing - [Label2] - Spacing - [Label3]</p>
  
  <p>Depending on the data displayed, the right 2 <code>UILabel</code>s can be hidden. If the first one is hidden it should look like this:<br></p>
  
  <p>[Label1] - Spacing - [Label3]</p>
  
  <p>Hiding the label is done in <code>tableView:cellForRowAtIndexPath:</code> in which i also call a method to set the appropriate constraint from the xib-file which can be accessed via an <code>IBOutlet</code>. This is working perfectly. But when rotating the device, the constraints are reloaded from the xib-file in which no constraint is <code>Installed</code>, but <code>updateConstraints</code> is not called again on my <code>UITableViewCell</code>-subclass, messing everything up.<br><br>
  One way to fix it would be by, instead of calling the method, which sets the appropriate constraint active, in <code>tableView:cellForRowAtIndexPath:</code> i could call it in <code>layoutSubviews</code> in my <code>UITableViewCell</code>-subclass. But i think you shouldn't update constraints in <code>layoutSubviews</code>.</p>