[PATCH] resolv: Remove support for RES_USE_INET6 and the inet6 option

[Florian Weimer]

* Florian Weimer:

> This functionality was deprecated in glibc 2.25.
>
> 2018-12-01  Florian Weimer  <fweimer@redhat.com>
>
> 	resolv: Remove support for RES_USE_INET6 and the inet6 option.

This patch is too large.  I missed some cleanups in the NIS and
nss_files code, so it is getting even larger.

I will post some of the changes separately, as smaller patches.

Thanks,
Florian