Add a macro that allows evaluating the macros from inner to outer

[tbu-]

This makes composing of macros easier and possible.

[huonw]

We now have a new guideline for filing issues, and language design feature requests should be on the RFCs repo. Feel free to reopen this there.

(BTW, this would be much improved with a code-example, to be 100% clear about what is being requested.)