add OpenBSD logging support

--- src/c/logger.c.orig	Fri Jul 31 18:11:51 2020
+++ src/c/logger.c	Fri Jul 31 18:12:14 2020
@@ -73,7 +73,7 @@ typedef long intptr_t;
   #include <sys/errno.h>
   #include <sys/fcntl.h>
  #elif defined(AIX) || defined(HPUX) || defined(MACOSX)
- #elif defined(FREEBSD)
+ #elif defined(FREEBSD) || defined(OPENBSD)
   #include <sys/param.h>
   #include <errno.h>
  #else /* LINUX */