* [tests][generator] Port XI/Classic tests to XI/Unified.
* [tests][generator] Comment out code triggering previously unknown bugs.
These tests makes the generator fail:
error BI0000: Unexpected error - Please file a bug report at http://bugzilla.xamarin.com
System.NullReferenceException: Object reference not set to an instance of an object
at Generator.GetSetterExportAttribute (System.Reflection.PropertyInfo pinfo) [0x0002e] in /work/maccore/master/xamarin-macios/src/generator.cs:1981
at Generator.Go () [0x007e3] in /work/maccore/master/xamarin-macios/src/generator.cs:2162
at BindingTouch.Main2 (System.String[] args) [0x010b2] in /work/maccore/master/xamarin-macios/src/btouch.cs:435
at BindingTouch.Main (System.String[] args) [0x0001d] in /work/maccore/master/xamarin-macios/src/btouch.cs:77
at System.Environment.get_StackTrace () [0x00000] in /work/maccore/master/xamarin-macios/_ios-build/Library/Frameworks/Xamarin.iOS.framework/Versions/git/src/mono/mcs/class/corlib/System/Environment.cs:321
at ErrorHelper.ShowInternal (System.Exception e) [0x000dc] in /work/maccore/master/xamarin-macios/src/error.cs:200
at ErrorHelper.Show (System.Exception e) [0x00027] in /work/maccore/master/xamarin-macios/src/error.cs:151
at BindingTouch.Main (System.String[] args) [0x0002b] in /work/maccore/master/xamarin-macios/src/btouch.cs:79
This has been filed as https://bugzilla.xamarin.com/show_bug.cgi?id=52664.
* [tests][generator] Comment out code triggering previously unknown bugs.
This has been filed as https://bugzilla.xamarin.com/show_bug.cgi?id=52665.
* [generator] Have WrapAttribute generate virtual members
WrapAttribute now has a boolean optional parameter named isVirtual,
this instructs the generator to add the virtual keyword to generated
members.
This is useful when fixing breaking changes so we can keep the wrong
signature generated instead of having manual code files.
* [docs] Add docs about virtual to WrapAttribute