Merge branch 'master' into stress_tests_new

.gitignore

BUILD

Makefile

binding.gyp

build.yaml

examples/objective-c/helloworld/HelloWorld.podspec

...jective-c/helloworld/HelloWorld.xcodeproj/project.pbxproj

examples/objective-c/helloworld/Podfile

examples/objective-c/helloworld/main.m

gRPC.podspec

src/core/channel/client_uchannel.c

src/core/channel/client_uchannel.h

src/core/client_config/subchannel.c

src/core/client_config/subchannel.h

src/core/iomgr/closure.c

src/core/iomgr/closure.h

src/core/iomgr/executor.c

src/core/iomgr/executor.h

src/core/iomgr/resolve_address_posix.c

src/core/iomgr/resolve_address_windows.c