Fixing GetTickCount.

There's likely a better way to do this (on demand), but this works for now.

src/xenia/kernel/xboxkrnl_module.h

@@ -31,6 +31,7 @@ class XboxkrnlModule : public XKernelModule {
   int LaunchModule(const char* path);
 
  private:
+  HANDLE timestamp_timer_;
 };
 
 }  // namespace kernel