Update from 2.8.0-rc3 to 2.8.0-rc4.
--[ Redis 2.8 Release Candidate 4 (2.7.104) ] Release date: 30 Aug 2013
This is the fourth release candidate of Redis 2.8 (official version is 2.7.104).
Important bugs fixed inside.
# UPGRADE URGENCY: HIGH because of the EVAL memory leak.
* [FIX] Fixed a serious EVAL memory leak in the Lua stack.
* [FIX] Fixed server startup when no IPv6 address exists in any interface.
* [FIX] Send MISCONFIG error when BGSAVE fails because can't fork.
* [FIX] Memory efficiency with large (> a few kbytes) values improved
* [NEW] DEBUG SDSLEN for sds memory debugging.