Makes project manager never initialize mono debug.

The heuristic whether we're in the project manager inside GDMono
didn't work if the project manager was launched by not having any path
to run.

This is fixed now by making a Main::is_project_manager().

main/main.h

@@ -56,6 +56,7 @@ public:
 	static bool iteration();
 	static void cleanup();
 	static void force_redraw();
+	static bool is_project_manager();
 };
 
 #endif