Merge github.com:grpc/grpc into grand-unified-closures

examples/node/README.md

include/grpc/impl/codegen/port_platform.h

src/csharp/Grpc.Core.Tests/project.json

src/csharp/Grpc.Core/Internal/NativeExtension.cs

src/csharp/Grpc.Examples.MathClient/project.json

src/csharp/Grpc.Examples.MathServer/project.json

src/csharp/Grpc.Examples.Tests/project.json

src/csharp/Grpc.Examples/project.json

src/csharp/Grpc.HealthCheck.Tests/project.json

src/csharp/Grpc.IntegrationTesting.Client/project.json

src/csharp/Grpc.IntegrationTesting.QpsWorker/project.json

src/csharp/Grpc.IntegrationTesting.Server/project.json

src/csharp/Grpc.IntegrationTesting.StressClient/project.json

src/csharp/Grpc.IntegrationTesting/project.json

src/csharp/build_packages_dotnetcli.sh

src/node/README.md

src/php/ext/grpc/call.c

src/php/ext/grpc/call_credentials.c

src/php/ext/grpc/channel.c

src/php/ext/grpc/channel_credentials.c