Merge github.com:grpc/grpc into simpler-cq

BUILD

Makefile

build.json

doc/interop-test-descriptions.md

gRPC.podspec

include/grpc++/credentials.h

include/grpc++/server.h

include/grpc++/server_builder.h

include/grpc/grpc_security.h

src/core/channel/census_filter.c

src/core/channel/http_client_filter.c

src/core/channel/http_server_filter.c

src/core/httpcli/httpcli.h

src/core/security/client_auth_filter.c

src/core/security/credentials.c

src/core/security/jwt_verifier.c

src/core/security/jwt_verifier.h

src/core/surface/call.c

src/core/surface/channel.c

src/core/surface/server.c