Merge pull request #2643 from jtattermusch/csharp_timeouts

src/compiler/csharp_generator.cc

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

src/csharp/Grpc.Core.Tests/Internal/TimespecTest.cs

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

src/csharp/Grpc.Core/Call.cs

src/csharp/Grpc.Core/Calls.cs

src/csharp/Grpc.Core/ClientBase.cs

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

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

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

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

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

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

src/csharp/Grpc.Examples.Tests/MathClientServerTests.cs

src/csharp/Grpc.Examples/MathGrpc.cs

src/csharp/Grpc.Examples/MathServiceImpl.cs

src/csharp/Grpc.HealthCheck/HealthGrpc.cs

src/csharp/Grpc.IntegrationTesting/TestGrpc.cs

src/csharp/ext/grpc_csharp_ext.c