Merge pull request #3765 from jboeuf/core_creds_api_change

Makefile

build.yaml

doc/grpc-auth-support.md

examples/cpp/cpptutorial.md

examples/cpp/helloworld/README.md

examples/cpp/helloworld/greeter_async_client.cc

examples/cpp/helloworld/greeter_client.cc

examples/cpp/route_guide/route_guide_client.cc

include/grpc++/channel.h

include/grpc++/client_context.h

include/grpc++/create_channel.h

include/grpc++/security/credentials.h

include/grpc++/support/channel_arguments.h

include/grpc/grpc_security.h

src/core/security/client_auth_filter.c

src/core/security/credentials.c

src/core/security/credentials.h

src/core/security/google_default_credentials.c

src/core/security/security_connector.c

src/core/security/security_connector.h