"require" clauses need to be able to take generic types

[ericlippert]

The require clauses have the grammars:

    require-extends-clause:
      require  extends  qualified-name  ;

    require-implements-clause:
      require  implements  qualified-name  ;

But we wish to allow parsing

class Foo<T> { }
trait Bar { 
    require extends Foo<int>; 
}

which does note match that grammar. The grammar should be updated to allow more than just qualified names here.