Fixes #5072.
Also fixed some issues around LangVersion handling, which were found along the way.

Fixes #4924.

Support multi-dimensional arrays of modified types.

Properly ref count diagnostic taggers.

Disable checks for non-compliant overloading for extension methods to match VS2013 behavior

Fix Native View tests on x64

Pointer width was hardcoded - switched to using ```PointerToString```.

Bonus: Fix cast exception in attempt to report the failure.
Bonus: Make Native View hex lowercase to match the rest of the
ResultProvider.

Don't include `public` accessiblity modifier in completion inside an interface

Escape System.Delegate when it is committed without qualification

Fixes #4405 

Copy current line if no selection

Fix #732. C# completion list must not suggest `public` as a potential
accessibility modifier to use inside an `interface { }` block;
otherwise, it produces code that does not compile.

Remove unnecessary call to AsImmutableOrEmpty

Move to readonly properties.

Enable FX 4.6 specific unification tests

Adjust implementation of OverloadResolution.GetParameterCounts to account for a situation when params parameter is used through a named argument.

Remove the SyntaxVisualizers from OpenSourceDebug

Remove the SyntaxVisualizers from OpenSourceDebug

Fixes #4623

The helper used to determine if completion should escape a type erroneously returned true for System.Delegate.

Remove unnecessary casts.

Add support to VB for custom modifiers associated with type arguments of generic types.

Fixes #4163.

Removing the SyntaxVisualizers from Roslyn.sln