Cherry pick: update go version in Dockerfile to 1.8

Link grpc_csharp_ext with static runtime.

Bump version to 1.2.1

Fix Python poll() server spinlock bug

Fix for using gem build/install

bump v1.2.x branch version to 1.2.1-pre2

Handle dropped ruby threads during active calls - client side

child thread - segfaults on mac

Fix ruby mingw build, add missing header

bump v1.2.x branch to 1.2.1-pre1

ruby add background channel state poller to handle disconnected transports

Going for 1.2.0

Add max_requests argument to server

If the server is already serving max requests, return RESOURCE_EXHAUSTED

Initialize GIL at startup

Advance ProtoCompiler version and fix podspecs