Merge branch 'master' into limit_cores

.gitignore

BUILD

Makefile

Rakefile

binding.gyp

build.yaml

doc/statuscodes.md

gRPC.podspec

grpc.def

grpc.gemspec

include/grpc/grpc_zookeeper.h

package.json

src/core/support/subprocess_windows.c

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

src/csharp/Grpc.Core/Grpc.Core.nuspec

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

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

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

src/csharp/ext/grpc_csharp_ext.c

src/php/ext/grpc/config.m4