Help stabilize a subset of Macros 2.0!

[derekdreery]

@durka

Hmm, okay that certainly seems like a step backwards since we often talk about macro_rules hygiene (imperfect though it is) as avoiding one of the mistakes of C macros. But yeah that makes sense why we don’t want to have expression macros yet!

It copy pastes the tokens not the characters so it is still better than C.