* Introduce a connection abstraction layer for all socket operations and
integrate it across the code base.
* Provide an optional TLS connections implementation based on OpenSSL.
* Pull a newer version of hiredis with TLS support.
* Tests, redis-cli updates for TLS support.
This is hiredis f225c276be7fd0646019b51023e3f41566633dfe
This update includes all changes that diverged inside of Redis since
the last update. This version also allows optional source address
binding for connections which we need for some Sentinel deployments.