Print raw types correctly.

The "For convenience, these are usable as stub implementations" bit has
generated surprisingly few angry letters, but I noticed today it blows it on
raw types. Or, used to blow it.
```scala
  /** As seen from class Sub, the missing signatures are as follows.
  *  For convenience, these are usable as stub implementations.
  *  (First one before this commitw as 'def raw(x$1: M_1)'
  */

  def raw(x$1: M_1[_ <: String]): Unit = ???
  def raw(x$1: Any): Unit = ???
```