Initial Alloy implementation.

This is a regression in functionality and performance, but a much better
foundation for the future of the project (I think). It can run basic
apps under an SSA interpreter but doesn't support some of the features
required to do real 360 apps yet.

src/xenia/cpu/cpu.h

@@ -11,8 +11,8 @@
 #define XENIA_CPU_CPU_H_
 
 #include <xenia/cpu/processor.h>
-
-// TODO(benvanik): conditionally include?
-#include <xenia/cpu/x64/x64_backend.h>
+#include <xenia/cpu/xenon_runtime.h>
+#include <xenia/cpu/xenon_thread_state.h>
+#include <xenia/cpu/xex_module.h>
 
 #endif  // XENIA_CPU_CPU_H_