build: remove bogus/deprecated inet_* tests

build: remove bogus/deprecated inet_* tests

These actually break configure on FreeBSD very subtly, because inet_aton
and __inet_aton are both detected, and then later other tests get
warnings about HAVE_INET_ATON being defined twice.

That said, they're incorrect to begin with since they detect alternative
functions but there is nothing in place to actually use these
alternates.

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
Acked-by: Greg Troxel <gdt@ir.bbn.com>
Acked-by: Feng Lu <lu.feng@6wind.com>
Acked-by: Paul Jakma <paul@jakma.org>
(cherry picked from commit 79f74962d20fa2c90df5a57335fc3b5e19bfeccf)