[SDK:NT] Improve ntdef.h and add guiddef.h

SDK/INC/NT/guiddef.h

@@ -0,0 +1,29 @@
+/*++
+
+Copyright (c) 2024, Quinn Stephens.
+Provided under the BSD 3-Clause license.
+
+Module Name:
+
+   guiddef.h
+
+Abstract:
+
+   Provides GUID definitions.
+
+--*/
+
+#ifndef _GUIDDEF_H
+#define _GUIDDEF_H
+
+#ifndef GUID_DEFINED
+#define GUID_DEFINED
+typedef struct _GUID {
+    ULONG Data1;
+    USHORT Data2;
+    USHORT Data3;
+    UCHAR Data4[8];
+} GUID;
+#endif
+
+#endif /* !_GUIDDEF_H */