promote a warning from -pedantic

[Dave Love]

You only get a warning about the following example from gcc 3.1 and
earlier if you use -pedantic, whereas at least two proprietary
compilers (fairly current Sun and SGI) actually give a fatal error.  I
think it should get a warning by default.

  void foo (float);
  void
  foo (bar)
       float bar;
  {
    return;
  }
  
For what it's worth, this is derived from a real example (changes to
Emacs).