Split libnu into libplatform, libamex

Going to add some ALLS stuff to libplatform and the ALLS hardware
does not contain an AMEX board.

amex/sram.h

@@ -0,0 +1,12 @@
+#pragma once
+
+#include <windows.h>
+
+DEFINE_GUID(
+        sram_guid,
+        0x741B5FCA,
+        0x4635,
+        0x4443,
+        0xA7, 0xA0, 0x57, 0xCA, 0x7B, 0x50, 0x6A, 0x49);
+
+HRESULT sram_hook_init(void);