Merge github.com:grpc/grpc into backoff_lib

BUILD

Makefile

build.yaml

gRPC.podspec

grpc.gemspec

include/grpc++/alarm.h

include/grpc++/channel.h

include/grpc++/impl/codegen/async_stream.h

include/grpc++/impl/codegen/async_unary_call.h

include/grpc++/impl/codegen/call.h

include/grpc++/impl/codegen/client_context.h

include/grpc++/impl/codegen/client_unary_call.h

include/grpc++/impl/codegen/completion_queue.h

include/grpc++/impl/codegen/core_codegen_interface.h

include/grpc++/impl/codegen/grpc_library.h

include/grpc++/impl/codegen/impl/async_stream.h

include/grpc++/impl/codegen/impl/status_code_enum.h

include/grpc++/impl/codegen/impl/sync.h

include/grpc++/impl/codegen/method_handler_impl.h

include/grpc++/impl/codegen/proto_utils.h