Merge github.com:grpc/grpc into can-we-be-single-threaded

BUILD

Makefile

build.yaml

gRPC.podspec

include/grpc++/impl/call.h

include/grpc++/security/auth_metadata_processor.h

include/grpc++/server.h

include/grpc/census.h

include/grpc/compression.h

include/grpc/grpc.h

include/grpc/grpc_security.h

include/grpc/support/port_platform.h

include/grpc/support/slice_buffer.h

src/core/census/grpc_filter.c

src/core/channel/compress_filter.c

src/core/channel/http_client_filter.c

src/core/channel/http_server_filter.c

src/core/client_config/subchannel.h

src/core/iomgr/pollset_multipoller_with_epoll.c

src/core/iomgr/pollset_multipoller_with_poll_posix.c