graph: light levels are now recalculated on every level change

inc/engine.h

@@ -448,6 +448,10 @@ public:
       return ptr->string;
    }
 
+   StringRef name () const {
+      return ptr->name;
+   }
+
    void set (float val) {
       engfuncs.pfnCVarSetFloat (ptr->name, val);
    }

inc/graph.h

@@ -167,6 +167,7 @@ private:
    bool m_hasChanged {};
    bool m_narrowChecked {};
    bool m_silenceMessages {};
+   bool m_lightChecked {};
 
    Vector m_learnVelocity {};
    Vector m_learnPosition {};