tests: On Unix, include <netinet/in.h> for IPPROTO_TCP
Otherwise, dbus doesn't compile on FreeBSD if the GLib-based tests are enabled (which suggests that no FreeBSD user has run those tests successfully).
We already include <netinet/in.h> in other places with no conditions or checks other than "is Unix", so apparently it's portable enough that specifically testing for its presence is not necessary. POSIX requires it to exist.
Signed-off-by: Simon McVittie firstname.lastname@example.org
(cherry picked from commit f0e526bc)