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.

  /** 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 = ???
Merge pull request #2598 from paulp/pr/raw-type-stubs

Print raw types correctly.