Added an extern "C" safeguard.

diff --git a/include/winbase.h b/include/winbase.h
index 47878fe..1f32748 100644
--- a/include/winbase.h
+++ b/include/winbase.h
@@ -3,6 +3,10 @@
 
 #include "windows.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #define WAIT_FAILED		0xffffffff
 #define WAIT_OBJECT_0		0
 #define WAIT_ABANDONED		STATUS_ABANDONED_WAIT_0
@@ -195,4 +199,8 @@
 BOOL32    WINAPI TerminateProcess(HANDLE32,DWORD);
 BOOL32    WINAPI TerminateThread(HANDLE32,DWORD);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif  /* __WINE_WINBASE_H */