Merge branch 'master' of github.com:google/grpc into docker_python

Makefile

build.json

include/grpc/grpc_security.h

include/grpc/support/host_port.h

src/core/debug/trace.c

src/core/iomgr/pollset_multipoller_with_poll_posix.c

src/core/iomgr/pollset_posix.c

src/core/iomgr/resolve_address_posix.c

src/core/iomgr/resolve_address_windows.c

src/core/iomgr/tcp_client_windows.c

src/core/iomgr/tcp_server_windows.c

src/core/security/auth.c

src/core/security/credentials.c

src/core/security/credentials.h

src/core/security/json_token.c

src/core/security/json_token.h

src/core/security/security_context.c

src/core/security/security_context.h

src/core/support/cpu_windows.c

src/core/support/host_port.c