pp: Fix macro expansion of typeof() argument

The first token of the PP typeof() argument was not being macro-expanded.
It should be though, because

* typeof() has no need not to do it. There's no need to check the type of
  #defines because they have none.

* The following cTypeOf() will do normal macro expansion for the rest of
  the tokens in the argument. It doesn't make sense to give special
  treatment to the first one.

* The old behaviour probably was the result of a buggy copy/paste from the
  defined() handling code which does need to avoid macro expansion of its
  argument's tokens in order to be able to check for macros.