Merge branch 'master' into sreek-epoll1

BUILD

CMakeLists.txt

Makefile

binding.gyp

build.yaml

config.m4

config.w32

gRPC-Core.podspec

grpc.gemspec

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

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

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

include/grpc++/support/slice.h

package.xml

src/core/ext/filters/client_channel/http_proxy.c

src/core/lib/iomgr/ev_epoll_limited_pollers_linux.c

src/core/lib/iomgr/ev_epollsig_linux.c

src/core/plugin_registry/grpc_cronet_plugin_registry.c

src/core/plugin_registry/grpc_plugin_registry.c

src/core/tsi/gts_transport_security.c