Tracking issue for assemblies to remove once we can do another breaking change, i.e. when we do Mono 6.0.

• nunit24, see Remove nunit24 from mono build and tree #12845
• IronPython, requested by maintainers a few times
• IBM.Data.DB2.dll, replaced by NuGet package
• ICSharpCode.SharpZipLib.dll, replaced by NuGet package, fixes problems like https://bugzilla.xamarin.com/show_bug.cgi?id=59304
• Compat.ICSharpCode.SharpZipLib.dll (old copy of above)
• Commons.Xml.Relaxng.dll, replaced by NuGet package
• Mono.C5.dll, replaced by NuGet package
• Mono.Data.Sqlite, replaced by https://github.com/praeclarum/sqlite-net
• RabbitMQ.Client.dll, replaced by NuGet package
• Mono.Http.dll, no idea what this is
• Very old copy of Rx.NET, replaced by NuGet packages
  • System.Reactive.Core.dll
  • System.Reactive.Debugger.dll
  • System.Reactive.Experimental.dll
  • System.Reactive.Interfaces.dll
  • System.Reactive.Linq.dll
  • System.Reactive.Observable.Aliases.dll
  • System.Reactive.PlatformServices.dll
  • System.Reactive.Providers.dll
  • System.Reactive.Runtime.Remoting.dll
  • System.Reactive.Windows.Forms.dll
  • System.Reactive.Windows.Threading.dll
  • external/rx submodule
• Very old copy of ASP.NET MVC framework, replaced by NuGet packages
  • System.Net.Http.Formatting.dll, fixes https://bugzilla.xamarin.com/show_bug.cgi?id=23668
  • System.Json.Microsoft.dll
  • System.Web.Http.dll
  • System.Web.Http.SelfHost.dll
  • System.Web.Http.WebHost.dll
  • System.Web.Mvc.dll
  • System.Web.Razor.dll
  • System.Web.WebPages.Deployment.dll
  • System.Web.WebPages.dll
  • System.Web.WebPages.Razor.dll
  • WebMatrix.Data.dll
  • Microsoft.Web.Infrastructure.dll
  • external/aspnetwebstack submodule