add PrimaryWorkspace concept in OOP

Handle additional cases in MemberSemanticModel.GetQueryEnclosingBinder

The problem is demonstrated by the following test case:

```
struct S { public int X, Y; }

class C
{
    public static void Main()
    {
        S s;
        s.X = 5;
        void Local()
        {
          s.Y = 10;
          System.Console.WriteLine(s);
        }
        Local(); // error CS0165: Use of unassigned local variable 's'
    }
}
```

Definite assignment should allow structs to be assigned piecewise
through a local function. The problem is that printing `s` is normally
regarded as a use of `s`, not its constituent fields. This causes the
analysis to effectively lose information about s.Y being assigned.

The fix is, when recording captured reads of possibly unassigned
structs in a local function, recursively record the possibly unassigned
constituent fields, rather than the struct variable.

Fixes #14097

Add System.Xml.ReaderWriter.dll to compilers vsix

Fix race condition writing assembly attribute file

MSBuild generates the TargetFrameworkAttribute file to the same path on
disk for equivalent combinations of TargetFrameworkIdentifier and
TargetProfile.  This means if two projects in a solution have equivalent
identifiers, their builds will race to write the same file to disk.

This is safe by virtue that the content of the file is the same in both
cases.  Hence it doesn't really matter who wins the race, both projects
see the same output.

This is frustrating though because even though it's safe, MSBuild still
isssue a warning when it happens.  This breaks our desire to have
warning free builds.

To fix this we will instead generate the file to the Obj\ProjectName
directory.  This means every project gets their own indepnedent copy of
the file, eliminating the race.

closes #10116

Add System.Runtime.InteropServices.RuntimeInformation to common nuget…

Merge dev15-rc2 into master

Adds Prerequisites to vsixmanifest templates

Adjust scope of variables declared within a ‘for’ condition and ‘for’ incrementors.

Don't manually construct strings.  It doesn't work for localization.

Variables declared within a ‘for’ condition are in scope only inside the condition, incrementors and body of the loop.
Variables declared within ‘for’ incrementors are in scope only inside the incrementors.

Related to #15630.

Remove call to SetProgress for performance reasons.

add missing codebase to VS for System.Xml.ReaderWriter.dll

Don't search for files looking for a predefined type when the type we're looking at is not predefined itself.

Wires up local functions through the semantic model and the SymbolId
service so the description is available to the editor.

Fixes #14163

Updating the Workspaces.Common nuspec to explicitly partition the des…

When local functions are declared in unsafe regions (unsafe statement,
unsafe member, unsafe type), their bodies should be considered unsafe
regions, even if unsafe is not a declaration modifier on the local
function.

Fixes #13172

Updating the Workspaces.Common nuspec to explicitly partition the desktop vs netstandard dependencies.

Combine deconstruction assignment and declaration, and support discards (merging to master)

Don't search for files looking for a predefined type when the type we're looking at is not predefined itself.

Update Roslyn dependencies to CoreFX 1.1 packages, specifically System.Reflection.Metadata 1.4.1

Manage diagnostics from open files only analyzers better

Analyzer install script fixes