proposed patch: protos for warning(), error()

[Jeffrey A Law]

  In message < 199804151508.LAA02991@caip.rutgers.edu >you write:
  > 	I'm not liking the ugliness factor here.  Let's not jump
  > through too many hoops and introduce too many oddities just to avoid
  > some one time editing.
Right.

  > 	I suggest that we "do the right thing".  I.e. include toplev.h
  > only in those files which use one or more of the relevant functions,
  > which link with toplev.o, and after including rtl.h/tree.h so we get
  > the proper definition for `tree'.
I'd tend to agree.  Let's try and do this right so that we don't
end up having to live with a wart later -- there's far too many
in the compiler already.

jeff