Initial impl of 'convert anonymous type to class' refactoring.

Track if a file contains a tuple expression or tuple type in our index.

Update PublishData.json for 15.8.x and 15.9.x

Merge dev15.8-preview4 to master

Update master's Versions.props to dev16 (temporarily 2.11.0)

The C# syntax tests were missing a reference to xunit.runner.visualstudio
which prevented them from working in the Test Explorer in 15.8 Preview.
Rather than just adding a reference to this one test, I've added a reference
to the root test utilities project, that almsot every test references, and
deleted the explicit references in the test leaf projects. This should
hopefully be a more robust method of using the XUnit VS test adapter.

Merge dev15.7.x to dev15.8-preview4

Handle null in AssemblyVersion attribute

Remove unused Maddog code