ltn12 should not export global table

[johnd0e]

https://github.com/lunarmodules/luasocket/blob/1fad1626900a128be724cba9e9c19a6b2fe2bf6b/src/ltn12.lua#L16-L19

module function exists in 5.1 (in 5.2 manual it is referenced as deprecated). Still nobody nowadays expect that module exports globals. Nor other (sub)modules of luasocket do that.

[alerque]

I agree this should be removed, but doing so will probably warrant a breaking release semver bump because it will not be a smooth upgrade path for anybody that was relying on this quirk.

[johnd0e]

I tend to view that as fixing a bug, which only requires a minor version bump. Of course, there may be someone who relies on the bug in their own workflow, but it is still a bug.

[catwell]

A long time ago almost all Lua modules used to export a global. ltn12 is a module from that era and used in a lot of places. So yes I can guarantee you changing this will break code, it should be done in a major revision.