[BUILD] fixed build of files including standard.h on OpenBSD

The file standard.h included netinet/in.h without including
sys/types.h. This broke build on OpenBSD.
diff --git a/include/common/standard.h b/include/common/standard.h
index b150445..8efda8a 100644
--- a/include/common/standard.h
+++ b/include/common/standard.h
@@ -23,6 +23,7 @@
 #define _COMMON_STANDARD_H
 
 #include <limits.h>
+#include <sys/types.h>
 #include <netinet/in.h>
 #include <common/config.h>
 #include <proto/fd.h>