build BUGFIX fix BSD builds, again, and cleanup

- just define _GNU_SOURCE and include sys/cdefs.h this gets everything
set the right way (no need to define _POSIX_C_SOURCE, etc).
- BSD requires more includes to get to sockaddr and AF_*
diff --git a/src/out.c b/src/out.c
index c368088..37beb69 100644
--- a/src/out.c
+++ b/src/out.c
@@ -12,8 +12,8 @@
  *     https://opensource.org/licenses/BSD-3-Clause
  */
 
-#define _GNU_SOURCE
-#define _POSIX_C_SOURCE 200809L /* strdup, vdprintf */
+#define _GNU_SOURCE /* asprintf, strdup */
+#include <sys/cdefs.h>
 
 #include "out.h"
 #include "out_internal.h"