for next time

[Stephen Weeks]

> > One  thing  I  meant to ask about before, but clearly didn't: do the .S files
> > produced really need to go through the preprocessor?
> 
> Currently, yes, they do need to go through the preprocessor, but only for
> the __LINE__ directive so that gc messages are printed correctly.

OK, then I vote for fixing this and keeping the line number ourselves.  That
will fix the other problem we had when compiling -g because of the debugger
wanting to look at the .s file.