Upgrade from 2.8.17 to 2.8.18.

<ChangeLog>

--[ Redis 2.8.18 ] Release date: 4 Dec 2014

UPGRADE URGENCY: LOW for both Redis and Sentinel. This release mostly

adds new features to Redis, and contains non critical
fixes.

• [FIX] Linenoise updated to be more VT100 compatible. (Salvatore Sanfilippo)
• [FIX] A number of typos fixed inside comments. (Various authors)
• [FIX] redis-cli no longer quits after long timeouts. (Matt Stancliff)
• [FIX] Test framework improved to detect never terminating scripts, cleanup instances on crashes. (Salvatore Sanfilippo)
• [FIX] PFCOUNT can be used on slaves now. (Salvatore Sanfilippo)
• [FIX] ZSCAN no longer report very small scores as 0. (Matt Stancliff, Michael Grunder, Salvatore Sanfilippo)
• [FIX] Don't show the ASCII logo if syslog is enabled. Redis is now an Enterprise Grade product. (Salvatore Sanfilippo)

• [NEW] EXPERIMENTAL: Diskless replication, for more info check the doc at http://redis.io/topics/replication. (Salvatore Sanfilippo).
• [NEW] Transparent Huge Pages detection and reporting in logs and LATENCY DOCTOR output. (Salvatore Sanfilippo)
• [NEW] Many Lua scripting enhancements: Bitops API, cjson upgrade and tests, cmsgpack upgrade. (Matt Stancliff)
• [NEW] Total and instantaneous Network bandwidth tracking in INFO.
• [NEW] DEBUG POPULATE two args form implemented (old form still works). The second argument is the key prefix. Default is "key:" (Salvatore Sanfilippo)
• [NEW] Check that tcp-backlog is matched by /proc/sys/net/core/somaxconn, and warn about it if not. (Salvatore Sanfilippo)

</ChangeLog>