CIOWin: Make Draw() non-const

Allows removing several const_cast usages within the codebase.

Runtime/GuiSys/CErrorOutputWindow.hpp

@@ -27,7 +27,7 @@ public:
   explicit CErrorOutputWindow(bool);
   EMessageReturn OnMessage(const CArchitectureMessage&, CArchitectureQueue&) override;
   bool GetIsContinueDraw() const override { return int(x14_state) < 2; }
-  void Draw() const override;
+  void Draw() override;
 };
 
 } // namespace urde