More refinement of the maps. Now the inner box won't have rooms in it and I can mark a region free of rooms. Rooms also have a guaranteed door.

src/algos/maze.hpp

@@ -10,6 +10,7 @@ namespace maze {
     std::vector<Room>& $rooms;
     std::vector<Point>& $dead_ends;
     std::unordered_map<Point, bool> $ends_map;
+    Room $no_rooms_region{0,0,0,0};
 
     Builder(Map& map) :
       $walls(map.$walls), $rooms(map.$rooms), $dead_ends(map.$dead_ends)
@@ -32,5 +33,6 @@ namespace maze {
     void open_box(size_t outer_size);
     void add_dead_end(Point at);
     bool room_should_exist(Room& room);
+    void make_doors();
   };
 }