host.conf.5: Clarify glibc versions in which spoof options were removed

The nospoof, spoofalert and spoof options as well as the
RESOLV_SPOOF_CHECK environment variable were all removed
from glibc in version 2.25 (with commit
7d68cdaa4f748e87ee921f587ee2d483db624b3d).

Signed-off-by: Nikola Forró <nforro@redhat.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
1 file changed