Add empty_loop lint

[chriscerie]

Closes #511.

This also lints for loops not involving tables, like

while true do end

[Kampfkarren]

This is fine, but it doesn't close #509. The bug I ran into there was I had a table, never did anything with it that would have led it to insert anything, then tried to loop over it, which would never have worked and we could statically analyze it.

[chriscerie]

This is fine, but it doesn't close #509. The bug I ran into there was I had a table, never did anything with it that would have led it to insert anything, then tried to loop over it, which would never have worked and we could statically analyze it.

Ah I misunderstood the issue. I created a new issue to track this.

[Kampfkarren]

Thanks!