Merge branch 'viewport' into docking

# Conflicts:
#	docs/TODO.txt

imgui_demo.cpp

@@ -2040,7 +2040,7 @@ static void ShowDemoWindowLayout()
         {
             ImGui::BeginChild("scrolling"); // Demonstrate a trick: you can use Begin to set yourself in the context of another window (here we are already out of your child window)
             ImGui::SetScrollX(ImGui::GetScrollX() + scroll_x_delta);
-            ImGui::End();
+            ImGui::EndChild();
         }
         ImGui::TreePop();
     }