Support for global recursive thunks

[raviqqe]

• Is it worth supporting global recursive thunks?
  • All global functions with no arguments can be considered as thunks and evaluated only once.

References

• Implemented in Global thunks #773.

  • pen/lib/hir-mir/src/module.rs

    Line 106 in 2c6fb6c

    Ok(if definition.lambda().arguments().is_empty() {

[raviqqe]

Implemented experimentally in #773.

Now, we cannot write infinite loops with top-level functions with no argument.