Adjust scope of locals declared within a Deconstruction Declaration Statement according to the latest design.

Improve parser error recovery for deconstruction declarations

Adjust scope of locals declared within a Deconstruction Declaration Statement according to the latest design.

Related to #12597.

Remove dependency on SemanticModel from FindRefs.

* Replace Windows style directory separator char with portable shim directory separator char in include file paths.

Fixes #11978

* Address PR feedback from tmat and attempt to replace the Windows stype separator char only if resolve fails with the original include path.

* Further cleanup/refactoring

Specify how the compiler identifies the core library.

Fix bogus cast.

Turn on /features:strict for all projects

Closure struct should not be abstract

Move to a unified SyntaxList model for C# and VB.

make OOP work with preview 5 (bcb2)

Add new packages to RedistPackageNames list...

It is not sufficient to list a package in PreReleaseOnlyPackages.  It must
also be listed in the "master" list.  I've updated the comment to reflect
that fact.

add some comments and make VS to explicitly crash on exception

Add support for TestImpact out-of-proc emit...