Correctly handle tail calls

[SquidDev]

Cobalt's handling of tail calls isn't entirely correct.

• Java functions are tail called. While this was considered a feature of LuaJ, it makes implementing Detailed argument errors #31 (or rather, the function name aspects of it) rather annoying. I don't think we gain anything from it, so I'd be in favour of removing this.

• Tail calls should be tracked in stack traces. Lua 5.3 prints (...tail calls...) (previous versions do (tail call): ?). This should be possible to do just by setting a tail call flag - I believe that's relatively similar to what PUC Lua does.