Include winerror.h if in Winelib mode.

diff --git a/include/mapicode.h b/include/mapicode.h
index 6a7a75b..702eef2 100644
--- a/include/mapicode.h
+++ b/include/mapicode.h
@@ -21,6 +21,10 @@
 #ifndef MAPICODE_H
 #define MAPICODE_H
 
+#ifndef __WINE__
+#include "winerror.h"
+#endif
+
 #define MAKE_MAPI_SCODE(sev,fac,code) \
     ( (((ULONG)(sev)<<31) | ((ULONG)(fac)<<16) | ((ULONG)(code))) )