merge with head and resolve conflicts

BUILD

build.json

doc/connection-backoff-interop-test-description.md

doc/interop-test-descriptions.md

gRPC.podspec

include/grpc++/client_context.h

include/grpc++/server_context.h

include/grpc/grpc.h

include/grpc/support/atm_gcc_atomic.h

include/grpc/support/atm_gcc_sync.h

include/grpc/support/atm_win32.h

src/core/census/grpc_context.c

src/core/census/grpc_context.h

src/core/client_config/subchannel.c

src/core/iomgr/fd_posix.c

src/core/iomgr/fd_posix.h

src/core/iomgr/tcp_server_posix.c

src/core/support/stack_lockfree.c

src/core/surface/call.c

src/core/surface/server.c