Merge github.com:grpc/grpc into microbench

BUILD

CMakeLists.txt

Makefile

build.yaml

doc/cpp-style-guide.md

include/grpc++/alarm.h

include/grpc++/channel.h

include/grpc++/ext/proto_server_reflection_plugin.h

include/grpc++/generic/async_generic_service.h

include/grpc++/generic/generic_stub.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/config.h

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

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

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

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

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