This commit broke things in interesting ways under FreeBSD. By adding these
default header files to every header check, a number of subsequent checks
failed (due to unsatisfied header file dependencies). This occured because
<netinet/in.h>, for example, requires <sys/types.h>. In other words, these
default includes are not autonomous and don't make workable defaults.
unistd.h \
unix.h \
utime.h \
-,,,[
-$ac_includes_default
-#if HAVE_NETINET_IN_H
-#include <netinet/in.h>
-#endif
-#if HAVE_ARPA_NAMESER_H
-#include <arpa/nameser.h>
-#endif
-])
+)