Merge github.com:grpc/grpc into uds

INSTALL

Makefile

include/grpc/grpc.h

include/grpc/support/port_platform.h

src/core/iomgr/socket_utils_linux.c

src/core/support/file_posix.c

src/core/support/log_posix.c

src/core/support/string_posix.c

src/core/support/sync_posix.c

src/core/support/time_posix.c

src/csharp/GrpcApi/MathExamples.cs

src/csharp/GrpcApi/MathGrpc.cs

src/csharp/GrpcApi/MathServiceImpl.cs

src/csharp/GrpcApiTests/MathClientServerTests.cs

src/csharp/GrpcCore/Call.cs

src/csharp/GrpcCore/Calls.cs

src/csharp/GrpcCore/Channel.cs

src/csharp/GrpcCore/ClientStreamingAsyncResult.cs

src/csharp/GrpcCore/GrpcCore.csproj

src/csharp/GrpcCore/GrpcEnvironment.cs