OpenBSD doesn't support timeb api
add SI_ASYNCIO define

Index: src/c/wrapper_unix.c
--- src/c/wrapper_unix.c.orig
+++ src/c/wrapper_unix.c
@@ -56,7 +56,9 @@
  #include <sys/filio.h> /* for FIONREAD */
 #endif
 #include <sys/resource.h>
+#ifndef OPENBSD
 #include <sys/timeb.h>
+#endif
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <sys/wait.h>
@@ -506,8 +508,10 @@ const TCHAR* getSignalCodeDesc(int code) {
         return TEXT("mesq state changed");
 #endif
 
+#ifdef SI_ASYNCIO
     case SI_ASYNCIO:
         return TEXT("AIO completed");
+#endif
 
 #ifdef SI_SIGIO
     case SI_SIGIO:
