Remove obsolete Solaris 8 support

[Richard Kenner]

> One of the nice things about gcc is that gcc usually still works,
> long after a vendor has abandoned a machine.  I rather like that gcc
> will just work, unlike vendor software, which often says, please buy
> a new machine.  One doesn't have to remove support in gcc for
> something, just because a vendor doesn't support it.  That said,
> truly crufty things, should go.

I agree.  If it's not causing a serious maintenance issue, I see no
reason to remove it.