Merge remote-tracking branch 'upstream/master' into circular_dependency_fix

BUILD

CMakeLists.txt

Makefile

binding.gyp

build.yaml

config.m4

gRPC-Core.podspec

grpc.gemspec

include/grpc/impl/codegen/grpc_types.h

package.xml

src/core/ext/client_channel/README.md

src/core/ext/client_channel/client_channel.c

src/core/ext/client_channel/client_channel_factory.c

src/core/ext/client_channel/client_channel_factory.h

src/core/ext/client_channel/lb_policy_factory.c

src/core/ext/client_channel/lb_policy_factory.h

src/core/ext/client_channel/resolver.c

src/core/ext/client_channel/resolver.h

src/core/ext/client_channel/resolver_factory.h

src/core/ext/client_channel/resolver_registry.c