Cleanup, commenting, trivial renaming
bump up limit on monomorphization
auto merge of #5077 : jbclements/rust/increase-monomorphization-depth-limit, r=catamorphism

It appears that using deriving_eq/auto_encode on ASTs bumps up against the "gee this looks like infinite unfolding" limit of 10 in monomorphization. Increasing it to 30 seems to solve this problem for me....

Also, commenting and a few renames.