Fixing Luarocks

Primarily, this fixes Luarocks. It also adds a shared, simple test to
Lua & Lua51, tidies up all formulae involved, and revisions all 4
lua-something formulae. Technically, this will work without revisioning
anything other than Luarocks, but doing it this way is much cleaner and
reduces the risk of a lingering lua screwing this update up for users.
Fixing Luarocks
lua: add 5.2.3_2 bottle.
lua51: update 5.1.5 bottle.
luajit: add 2.0.3_1 bottle.
luarocks: update 2.2.0_1 bottle.