Update from 2.6.7 to 2.6.8.
Add experimental support for lang/luajit, disabled by default.
UPGRADE URGENCY: MODERATE if you use Lua scripting. Otherwise LOW.
* [BUGFIX] Multiple fixes for EVAL (issue #872).
* [BUGFIX] Fix overflow in mstime() in redis-cli and benchmark.
* [BUGFIX] Fix Linux / PPC64 behavior by correcting endianess detection.
* [BUGFIX] Fix NetBSD build by defining _XOPEN_SOURCE appropriately.
* [BUGFIX] Added missing license and copyright in a few places.
* [BUGFIX] Better error reporting when fd event creation fails.