Merge branch 'master' into tsi_grpc

.pylintrc

BUILD

CMakeLists.txt

Makefile

binding.gyp

build.yaml

config.m4

config.w32

doc/environment_variables.md

doc/epoll-polling-engine.md

gRPC-Core.podspec

gRPC.podspec

grpc.gemspec

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

include/grpc++/support/slice.h

include/grpc/impl/codegen/grpc_types.h

package.xml

...rs/client_channel/resolver/dns/c_ares/dns_resolver_ares.c

...rs/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.c

...rs/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.h