Compile XDK code as C

It appears to be all C code (especially the non-C++ parts of the C
runtime, of course), so we'll compile it as such.

decompile/src/XDK/D3D.h

@@ -0,0 +1,35 @@
+/* JSRF Decompilation: XDK/D3D.h
+Direct3D8 declarations.
+*/
+
+#ifndef D3D_H
+#define D3D_H
+
+#include "Win32.h"
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+typedef DWORD D3DCOLOR;
+
+struct D3DVECTOR  {
+	float x, y, z   ;
+};
+struct D3DVECTOR4 {
+	float x, y, z, w;
+};
+
+struct D3DRECT {
+	LONG x1, y1, x2, y2;
+};
+
+
+#ifdef __cplusplus
+}
+#endif
+
+
+#endif