Fix Lua 5.2 compatability by using table.unpack

'unpack' is only on 5.1, in 5.2 it got moved to 'table.unpack'

This line gives us the proper 'unpack' based on what's in our
global namespace.

Author: moteus

test.lua

@@ -6,6 +6,8 @@ local cmsgpack = require "cmsgpack"
 local ok, cmsgpack_safe = pcall(require, 'cmsgpack.safe')
 if not ok then cmsgpack_safe = nil end
 
+local unpack = unpack or table.unpack
+
 passed = 0
 failed = 0
 skipped = 0