JSON spec makes escaping of forward slashes optional and many have
complained about the aesthetics of '\/'. Previously, we got this
behavior from the DataContractJsonSerializer and could not override
it, but now that the dependency has been removed, we can eliminate
the unnecessary escaping.

Generalize dynamic static-only restriction to include field initializers (was just ctor initializers)

* Ensure that we suppress compilation diagnostics reported in generated code when the analyzer is configured to analyze generated code, but not report diagnostics on generated code.

Fixes #11217

* Address PR feedback to improve performance of AnalyzerDriver.IsInGeneratedCode

* Address PR feedback and modify test

harden both DetectTypeCircularity and GetDependenceChain

* remove old syntax tree root tests

* fix vb tests

Ensure that we generated a CompilationCompletedEvent for compilations with no source files (example an empty VSIX projects).

Move lines appearing in PublicAPI.Unshipped.txt files to
PublicAPI.Shipped.txt files and re-sort the latter.

Note: VB scripting APIs and APIs for IOperation continue to remain
unshipped.

To prevent projects across the tree from having different dependencies, we unify
external package dependencies by creating empty C# projects that represent them.
We then make use of project.json package inheritance (where a project inherits
all packages dependencies from their dependencies) to unify it across the tree.

No projects outside of this tree, should be directly referencing versions of
these dependencies manually.

For this check-in I've tackled Metadata, Reflection, and DiaSymReader. Will tackle
the rest in future commits.

This reverts commit 92ff3f8d.

Make compiler produce the same Product Build, Major, Minor and Private Parts in VersionInfo as VS2013 compiler when Assembly ProductAssemblyFileVersionAttribute and AssemblyInformationalVersion contain invalid format. Also introduce warning diagnostic for AssemblyInformationalVersion with invalid version string

VB: Always import instance fields for an Enum type in order to be able to infer underlying type of its elements.

Address https://devdiv.visualstudio.com/DefaultCollection/DevDiv/_workitems?_a=edit&id=193333.

What's been done:
- All the RTM references have not been changed
- All the prerelease refs have been bumped
- All the projects with prerelease refs have been
  changed to use netstandard1.3 instead of dotnet5.4
- Crossgen has been updated to point to the new CLR directory
- The NuSpecs have been updated to use the new refs

There is also now a stand-alone project for referencing
CoreCLR that can be updated independently of corefx. It will
need to be added to the closed solution before the refs in
the existing projects can be removed.