Between grpc 1.2.x and 1.7.x there was an API change. The
previous MaxMsgSize is now a wrapper around MaxRecvMsgSize. This
change now sets the MaxRecvMsgSize and MaxSendMsgSize which need
to be set independently.
Adds an `unreleased` flag to the version if not building from HEAD of a
tag. The compatibility check is bypassed if the client or server are
unreleased.
fixes#2110