This reverts commit b37052d0.

The primary use of DefineConstants should be to append constant values,
not replace them.  Any time a replacement operation is used it prevents
us from establishing defines in our targets and pushing them down to all
affected projects.

  <Reference Include="xunit">
    <HintPath>..\..\..\packages\xunit.1.9.2\lib\net20\xunit.dll</HintPath>
  </Reference>

rather than the recently introduced:

  <Reference Include="..\..\..\packages\xunit.1.9.2\lib\net20\xunit.dll" /> (changeset 1397721)

     1. Removes the project reference to CommonScritpingTests.  This just existed to ensure the ReflectionEmit emmiter was present in the binaries directory.  Our main infrastructure already guarantees this by virtue of building all projects.
     2. Make the Emmiter load code tolerant of the ReflectionEmit Emitter not being present in binaries.  This is the case when building the Open directory only via OSS.
 (changeset 1396895)

This moves our settings / targets files into the Open directory.  These files are a referenced by virtually all of the projects in the Open directory and are a necessary part of the build process.  Making this change is a necessary step in removing the project scrubber.  (changeset 1396832)

This changes our projects to consume xUnit through NuGet instead of our checked in binaries in Closed\Tools\xUnit.  This is another step in removing project scrubber.  (changeset 1396548)

 Change Description:

     This change moves Roslyn off of our custom version of xUnit to an official release (xUnit 1.9.2):

     - Deletes all of the custom xUnit binaries from Closed\Tools\xUnit
     - Put a subset of the official 1.9.2 binaries with no name mangling into Closed\Tools\xUnit.
     - Rebuilt our custom xUnit GUI (named xunit.gui.custom) against 1.9.2 and put it in Closed\Tools\xUnit
     - Updated the targets file, RunTests.ps1 and Test.exe to refer to the updated binary names.
     - Changed the Roslyn unit tests to work on standard xUnit.

     The biggest part of the effort was the last part, getting the tests to run on standard xUnit.  The main issue here was many assumed they would be executed on a single STA thread and as a result cached many thread affinitized values into static fields.  Fixing this involved mostly finding the values and annotating them with [ThreadStatic].

     This does mean that MEF composition will happen several times during an xUnit run where before it happened only once.  That is unfortunate but doesn't seem to regress the suites in a significant way on my machine.  Using a multithreaded MEF container isn't an option here because the services end up caching thread affinitized WPF values.

     ForegroudThreadAffinitizedObject was the other largest change.  It's use of a static ctor to establish the foreground thread is dangerous and should be correctly addressed in a future change.  For now I added a method for tests to reset the identified foreground thread.

     More changes will be coming here for our use of xUnit.  But they should be smaller and more targetted (deleting the extra sources, a better build story for the GUI, etc ...).

     Note: Why 1.9.2 instead of 2.0?  We have several uses of custom xUnit extensibility that is not easily portable to 2.0.  Best path forward is to delete that extensibility since it isn't really adding much and move us directly onto 2.0 in a later check in.

 (changeset 1395675)

This changeset introduces the concept of a "global" nuget package. The references to the NuGet packages are inserted into the Open VSL.Settings.targets file, which is imported into every project in Roslyn. This ensures that every project automatically gets these "global" packages. (changeset 1386548)

Updates System.Collections.Immutable and System.Metadata.Reader to versions 1.1.33-beta and 1.0.18-beta, respectively.
     Updates VSMEF to the latest build from VSPRO_1.

     A few code fixes:
     - ImmutableArrayInterop is gone
       - in product we used in a couple of places where we now just create a copy of the byte[] (MetadataWriter)
       - test infrastructure uses a workaround with explicitly laid out union to avoid copies of large metadata blobs
     - EditorTestApp class was incorrectly importing MEF components resulting in a cycle. The new VSMEF reports such errors. (changeset 1385613)

We had a number of projects that included the StyleCop NuGet package only to also disable StyleCop. We also had some projects that were referencing assemblies out of packages but didn't say so in packages.config, or had stuff in packages.config not reflected in the actual project file. (changeset 1378738)

***NO_CI***
 (changeset 1367677)

***NO_CI***
 (changeset 1356181)

This also updates Microsoft.Net.ToolsetCompiler to the corresponding version. (changeset 1355122)

When our projects were last updated to a newer version of Microsoft.Net.ToolsetCompilers, NuGet didn't replace the old version--it just put the new version next to it. Every project ended up referencing both versions, and which set of compiler binaries "won" depended on the order they appeared in the project file. So different projects built with different compilers.

This change strips out all references to the old version. (changeset 1352054)

***NO_CI***
 (changeset 1341082)

Removes workarounds for portability bugs 967430 and 797360 - the underlying issues in the project system have been fixed.
Removes explicit references to portable facade assemblies (System.IO, System.Runtime, etc.).
 (changeset 1336570)

Change projects to reference the Proprietary Resources NuGet package versus the project. (changeset 1331358)

Update the version of the toolset compilers used for build and make sure that all projects are using the toolset NuGet. (changeset 1330804)

messages.

The new native client is written in C++11 to be more maintainable and
forward-looking. The native client is a static library, which is now
linked into the csc2 and vbc2 projects instead of having a single csc2.cpp
file which is shared between the two projects and built for each based on
a preprocessor definition.

The MSBuildTask is also configured to use csc2/vbc2 and feature no extra
code for Roslyn, which will prevent us from having to maintain both a
native and a managed version of the client. (changeset 1325415)

MSBuild unconditionally overwrites the value of BuildDependsOn in Microsoft.Common.CurrentVersion.targets:
  <PropertyGroup>
    <BuildDependsOn>
      BeforeBuild;
      CoreBuild;
      AfterBuild
    </BuildDependsOn>
  </PropertyGroup>

So NuGet.targets needs to be included after Microsoft.Common.CurrentVersion.targets.  Otherwise, the RestorePackages build target won't run.

 (changeset 1311037)

The new native client is written in C++11 to be more maintainable and forward-looking. The native client is a static library, which is now linked into the csc2 and vbc2 projects instead of having a single csc2.cpp file which is shared between the two projects and built for each based on a preprocessor definition.

The MSBuildTask is also configured to use csc2/vbc2 and feature no extra code for Roslyn, which will prevent us from having to maintain both a native and a managed version of the client. (changeset 1307711)

Previously the command line tests were looking in various directories for csc.exe/vbc.exe. Instead, add a reference to csc/vbc project to the command line unit test assembly, so that we always test what we build and not depend on directories outside of Roslyn.
To make it easy to test the default .rsp file this change links it into the command line unit test project and includes it to resources. The tests then extract the .rsp from the resources and save it to a temp file for testing.
 (changeset 1285693)

rcsc to csc
rcsi to csi
rcsc2 to csc2
rvbc to vbc
rvbi to vbi
rvbc2 to vbc2
 (changeset 1285266)

Splits Microsoft.CodeAnalysis, Microsoft.CodeAnalysis.CSharp and Microsoft.CodeAnalysis.VisualBasic into portable and desktop assemblies.

Existing Core\Source, CSharp\Source and VisualBasic\Source directories are renamed to Core\Portable, CSharp\Portable and VisualBasic\Portable.
New sibling Desktop folders are added and non-portable source is moved there.
"System.Runtime" references has to be removed in order for the portable project system magic to automatically add facade references.
 (changeset 1281686)

Adds support for method body visualization to MetadataVisualizer. (changeset 1236565)

Update Test Resources Nuget package to Microsoft.CodeAnalysis.Test.Resources.Proprietary.0.6.4033103-beta
 (changeset 1219704)

Update the Roslyn Toolset to a version with an official, signed, NuGet package.

The new package is Microsoft.Net.ToolsetCompilers.0.7.4032713-beta.nupkg. (changeset 1217415)

Update Test Resources Nuget package to Microsoft.CodeAnalysis.Test.Resources.Proprietary.0.7.4032713-beta

Not strictly necessary, but it would be nice to be on the same build as the toolset compiler. (changeset 1217394)

The new package is Microsoft.Net.ToolsetCompilers.0.7.4032713-beta.nupkg. (changeset 1217346)

Update Test Resources Nuget package to Microsoft.CodeAnalysis.Test.Resources.Proprietary.0.7.4032705-beta (changeset 1216765)