Speculative 64-bit warning fix (#668)

imgui_demo.cpp

@@ -1803,7 +1803,7 @@ static void ShowExampleAppConstrainedResize(bool* p_open)
     struct CustomConstraints // Helper functions to demonstrate programmatic constraints
     {
         static void Square(ImGuiSizeConstraintCallbackData* data) { data->DesiredSize = ImVec2(IM_MAX(data->DesiredSize.x, data->DesiredSize.y), IM_MAX(data->DesiredSize.x, data->DesiredSize.y)); }
-        static void Step(ImGuiSizeConstraintCallbackData* data)   { float step = (float)(int)data->UserData; data->DesiredSize = ImVec2((int)(data->DesiredSize.x / step + 0.5f) * step, (int)(data->DesiredSize.y / step + 0.5f) * step); }
+        static void Step(ImGuiSizeConstraintCallbackData* data)   { float step = (float)(int)(intptr_t)data->UserData; data->DesiredSize = ImVec2((int)(data->DesiredSize.x / step + 0.5f) * step, (int)(data->DesiredSize.y / step + 0.5f) * step); }
     };
 
     static int type = 0;