errno, h_errno and _res

[Roland McGrath]

Unless I missed something, I didn't see any rationale about your moving the
TLS symbols to GLIBC_PRIVATE.  

> Shouldn't we change those 3 even in non-TLS builds from errno@@GLIBC_2.0
> to errno@GLIBC_2.0 etc., so that new programs accessing these directly
> simply don't link anymore?

I've done this.  But libpthread.so needs to refer to them, so I will have
to do some kind of funny business to make that work.