Merge branch 'master' into mono-build

tests/Avalonia.Layout.UnitTests/Properties/AssemblyInfo.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
 using System.Reflection;
+using Xunit;
 
 [assembly: AssemblyTitle("Avalonia.Layout.UnitTests")]