Fix type alias

We forgot the type parameters, which caused from-tasty and pickling tests
to fail. We should probably disallow these forms of aliases and check for
this.

Author: odersky

tests/pos/main-method-scheme.scala

@@ -22,7 +22,7 @@ class main(progName: String, args: Array[String], docComment: String) extends Ma
 
   def this() = this("", Array(), "")
 
-  type ArgumentParser = util.FromString
+  type ArgumentParser[T] = util.FromString[T]
 
   /** A buffer of demanded argument names, plus
    *   "?"  if it has a default