Upgrade tests to use Xunit 2.0
Fix DEBUG constant name
Prepare metadata reader tests to be portable
Build metadata reader tests as PCL
Add System.IO.Pipes source code
Merge branch 'xunit2' into test_on_coreclr

Conflicts:
	src/System.Numerics.Vectors/tests/Matrix3x2Tests.cs
	src/System.Numerics.Vectors/tests/Matrix4x4Tests.cs
	src/System.Numerics.Vectors/tests/PlaneTests.cs
	src/System.Numerics.Vectors/tests/QuaternionTests.cs
	src/System.Numerics.Vectors/tests/Vector2Tests.cs
	src/System.Numerics.Vectors/tests/Vector4Tests.cs
	src/System.Reflection.Metadata/tests/TestUtilities/WorkItemAttribute.cs
Merge branch 'mdreader-portable-tests' into test_on_coreclr

Conflicts:
	src/System.Reflection.Metadata/tests/Metadata/MetadataReaderTests.cs
	src/System.Reflection.Metadata/tests/System.Reflection.Metadata.Tests.csproj
	src/System.Reflection.Metadata/tests/packages.config
Merge pull request #269 from mellinoe/add-pipes

Add System.IO.Pipes source code
Updated Readme to include Pipes

Added a short description of System.IO.Pipes to the readme list.
Update XML tests to register a code page provider

Required for the tests to pass on .NET Core.
Improve ActionBlock.Post perf for SingleProducerConstrained
Make SpscTargetCore.OfferMessage use Post method on fast path
Remove TargetCore.Post method as it doesn't add to perf.
Disable 4 PLINQ tests against GitHub issue corefx/240
Disable MetadataReader test against GitHub issue corefx/260
Disable 4 MetadataReader tests against GitHub issue corefx/264
Convert TPL tests to a portable library compiled against contracts.
Stop Micr..Win32.Registry from copying contract assemblies to output
Stop SIMD tests from copying contract assemblies to output
Include referenced fx libraries in packages.config for SIMD tests