Add ARM9 exception vectors feature from @TuxSH

exceptions/arm9/source/handlers.h

@@ -0,0 +1,14 @@
+/*
+*   handlers.h
+*       by TuxSH
+*
+*   This is part of Luma3DS, see LICENSE.txt for details
+*/
+
+#pragma once
+
+void setupStack(u32 mode, void *stack);
+void FIQHandler(void);
+void undefinedInstructionHandler(void);
+void dataAbortHandler(void);
+void prefetchAbortHandler(void);