include/winternl.h: Guard preprocessor use of _WIN32_WINNT

[Gerald Pfeifer]

Last for now, all but one or two cases addressed.

Gerald

ChangeLog:
Guard preprocessor use of _WIN32_WINNT.

diff --git a/include/winternl.h b/include/winternl.h
index d38f49c..e7b9b9a 100644
--- a/include/winternl.h
+++ b/include/winternl.h
@@ -1670,7 +1670,7 @@ typedef struct _RTL_HANDLE_TABLE
 #define FILE_PIPE_SERVER_END            0x00000001
 #define FILE_PIPE_CLIENT_END            0x00000000
 
-#if (_WIN32_WINNT >= 0x0501)
+#if defined(_WIN32_WINNT) && (_WIN32_WINNT >= 0x0501)
 #define INTERNAL_TS_ACTIVE_CONSOLE_ID ( *((volatile ULONG*)(0x7ffe02d8)) )
 #endif /* (_WIN32_WINNT >= 0x0501) */