Return address handling. Not happy with the design, but it (sorta) works.

src/xenia/cpu/processor.cc

@@ -117,7 +117,7 @@ int Processor::Execute(XenonThreadState* thread_state, uint64_t address) {
   context->lr = lr;
 
   // Execute the function.
-  fn->Call(thread_state);
+  fn->Call(thread_state, lr);
   return 0;
 }