Upgrade from 2.8.3 to 2.8.4.
# UPGRADE URGENCY: MODERATE for Redis and Sentinel.
* [FIX] Makefile compatibility with non common make variants improved.
* [FIX] SDIFF crash in very unlikely to trigger state fixed.
* [FIX] Config rewriting fixed: don't wipe options unknown to the rewrite
* [FIX] Set TCP port to 0 works again to disable TCP networking.
* [FIX] Fixed replication with old Redis instances as masters by not
sending REPLCONF ACK to them.
* [FIX] Fix keyspace notifications rewrite and CONFIG GET output.
* [FIX] Fix RESTORE TTL handling in 32 bit systems (32 bit overflow).
* [NEW] Sentinel now has a run time configuration API.
* [NEW] Log when we lost connection with master or slave.
* [NEW] When instance is turned from slave to master now inherits the
old master replication offset when possible. This improves the
Sentinel failover procedure.