Move main executable source to its own directory (#248)

* Move main executable files to their own directory

* Adapt the build to the new file structure

... and fix some weird #include's that were relying on the project root
being an include directory.

Ja2/gameloop.h

@@ -0,0 +1,26 @@
+#ifndef __GAMELOOP_
+#define __GAMELOOP_
+
+#include "Types.h"
+
+// main game loop systems
+#define INIT_SYSTEM										0
+
+#define	NO_PENDING_SCREEN			0xFFFF
+
+
+extern BOOLEAN InitializeGame(void);
+extern void	ShutdownGame(void);
+extern void	GameLoop(void);
+
+// handle exit from game due to shortcut key
+void HandleShortCutExitState( void );
+
+void SetPendingNewScreen( UINT32 uiNewScreen );
+
+#ifdef USE_HIGHSPEED_GAMELOOP_TIMER
+	struct InputAtom;
+	void HandleDefaultEvent(InputAtom *Event);
+#endif
+
+#endif