Split libnu into libplatform, libamex

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

amex/gpio.h

@@ -0,0 +1,12 @@
+#pragma once
+
+#include <windows.h>
+
+DEFINE_GUID(
+        gpio_guid,
+        0xE9A26688,
+        0xF522,
+        0x44FA,
+        0xBF, 0xEE, 0x59, 0xDD, 0x16, 0x15, 0x56, 0x6C);
+
+void gpio_hook_init(void);