Merge github.com:grpc/grpc into credit

src/core/surface/channel.c

src/core/surface/init.c

src/core/surface/init.h

src/core/surface/server.c

src/csharp/.gitignore

src/csharp/Grpc.Core.Tests/PInvokeTest.cs

src/csharp/Grpc.Core/ChannelArgs.cs

src/csharp/Grpc.Core/Grpc.Core.csproj

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

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

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

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

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

...csharp/Grpc.Core/Internal/ClientStreamingInputObserver.cs

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

...sharp/Grpc.Core/Internal/ServerStreamingOutputObserver.cs

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

src/csharp/Grpc.Core/OperationFailedException.cs

src/csharp/Grpc.Core/ServerCallHandler.cs

src/csharp/Grpc.Core/Status.cs