Possibly handle macros in fold

[catamorphism]

See the item_mac case in fold::noop_fold_item_underscore.

[pnkfelix]

Not critical for 0.6; de-milestoning

[catamorphism]

@jbclements -- does it make sense for the AST fold to visit macros? Or is the current code correct?

[jbclements]

From my perspective: yes, definitely. In particular, I'm going to want ident-folds to hit the idents inside of macro invocations. Could it break code to add this traversal? Well, the only place you're going to see unexpanded macro invocations is prior to expansion, and the only thing inside of macro invocations is tokens, so it seems very unlikely.

To summarize: yes, this fold should visit macro invocations.

[catamorphism]

In that case, nominating for milestone 5, production-ready

[graydon]

accepted for production-ready milestone

[jbclements]

I've implemented this in a local branch, I expect to push it soon (next two days)

[jbclements]

done, now. FIXME removed downstream.