- Backend update from Raze

Mostly cleanup and better separation of game/backend concerns.

src/common/engine/i_interface.cpp

@@ -1,6 +1,8 @@
 #include "i_interface.h"
+#include "st_start.h"
 
 // Some global engine variables taken out of the backend code.
+FStartupScreen* StartWindow;
 SystemCallbacks sysCallbacks;
 FString endoomName;
 bool batchrun;