update Xcode project, fix some warnings, update android icons, ignore unrecognized files in the doc browser

src/node_canvas.cpp

@@ -135,7 +135,7 @@ void NodeCanvas::draw()
             if (m_canvas->m_layers[layer_index].m_opacity == .0f)
                 continue;
 
-            int z = (int)m_canvas->m_order.size() - i;
+            int z = (int)(m_canvas->m_order.size() - i);
             auto plane_mvp_z = proj * camera * 
                 glm::scale(glm::vec3(z + 1)) * 
                 glm::eulerAngleYXZ(yaw, pitch, roll) *
@@ -362,7 +362,6 @@ void NodeCanvas::handle_resize(glm::vec2 old_size, glm::vec2 new_size)
 
 kEventResult NodeCanvas::handle_event(Event* e)
 {
-    static std::vector<CanvasMode>* old_mode = nullptr;
     Node::handle_event(e);
     MouseEvent* me = static_cast<MouseEvent*>(e);
     KeyEvent* ke = static_cast<KeyEvent*>(e);