Upgrade from 2.8.19 to 3.0.0.
Merge all changes from databases/redis-devel to databases/redis.

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Redis 3.0 release notes

--[ Redis 3.0.0 ] Release date: 1 Apr 2015

What's new in Redis 3.0 compared to Redis 2.8?

• Redis Cluster: a distributed implementation of a subset of Redis.
• New "embedded string" object encoding resulting in less cache misses. Big speed gain under certain work loads.
• AOF child -> parent final data transmission to minimize latency due to "last write" during AOF rewrites.
• Much improved LRU approximation algorithm for keys eviction.
• WAIT command to block waiting for a write to be transmitted to the specified number of slaves.
• MIGRATE connection caching. Much faster keys migraitons.
• MIGARTE new options COPY and REPLACE.
• CLIENT PAUSE command: stop processing client requests for a specified amount of time.
• BITCOUNT performance improvements.
• CONFIG SET accepts memory values in different units (for example you can use "CONFIG SET maxmemory 1gb").
• Redis log format slightly changed reporting in each line the role of the instance (master/slave) or if it's a saving child log.
• INCR performance improvements.

Refactoring changes (no new features nor bug fixes)

• Blocking operations full refactoring (blocked.c)
• Client output buffer memory tracking refactored.

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