[nem-en] Feature request: Matching !null

[vc]

   > Why introduce new syntax if this is possible now by:
   > 
   > def a = array ["aa", null, "bbv"];
   > foreach (x when x != null in a)
   >     System.Console.WriteLine (x);
   
   Hm... You are right! Who could think? :)
   
   But will be nice if it will be reflected in foreach examples.
   http://nemerle.org/Quick_Guide
   
   Vlad