Add namespace aliases and :: operator

[bfiete]

using forwpf = System.Windows;
global::System.Console.WriteLine("Using global alias");

In C#: https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/operators/namespace-alias-qualifier

[bfiete]

'::global' implemented at 958a1630aaeb54b68b6e3bea7cafac8d7b1e6351