title: Invalid resource directory name for values with country code
body: <p>I have an android app in more languages.
  If I have a folder named: <strong>values-en</strong> I have no error and everything is working fine. </p>
  
  <p>If I rename the name of the dir to <strong>values-en_GB</strong> i got this error: <code>android-apt-compiler: [NAMEOFAPP] invalid resource directory name: [path]\res/values-en_GB</code></p>
  
  <p>Why is this invalid? or what I should do to have for same language (in this example en) different values depend of the location (in this example US or GB)</p>
  
  <p>I am using Idea 12, Java 1.7, Android 4.2</p>