GCC headers and DJGPP port

[Mark E.]

> > In any case, the following headers out of the above list seem
> > especially dangerous:
> > 
> >   - errno.h
> >   - limits.h
> >   - assert.h
> >   - math.h

These are fixincluded headers. Or at least they aren't in the replacement 
header directory. Don't worry about these.

> >   - stddef.h
> > 
This one is along with:
iso646.h
stdarg.h
stdbool.h
varargs.h