Add support for anonymous struct/unions on compilers that implement it.

diff --git a/include/ntddk.h b/include/ntddk.h
index 919287e..d89eb46 100644
--- a/include/ntddk.h
+++ b/include/ntddk.h
@@ -20,10 +20,11 @@
 #undef Status	/* conflict with X11-includes*/
 
 typedef struct _IO_STATUS_BLOCK 
-{	union 
-	{ NTSTATUS Status;
+{
+	union {
+	  NTSTATUS Status;
 	  PVOID Pointer;
-	} u;
+	} DUMMYUNIONNAME;
 	ULONG_PTR Information;
 } IO_STATUS_BLOCK, *PIO_STATUS_BLOCK;