Purge `map(|&x| x)` et al

[Gankra]

Option and IteratorExt both have .cloned() which is sugar for this operation.

AKA

• .map(|x| *x)
• .map(|x| x.clone())
• .map(|x| (*x).clone()) (yes, really)

[untitaker]

There are two or three occurrences of code like this:

edible.iter().map(|x| TokenType::Token(x.clone()))

Should they also be replaced?

Also, src/doc/style/style/naming/containers.md contains the same code again.

[Gankra]

It can be converted to edible.iter().cloned().map(TokenType::Token). Whether that is better is a matter of taste.

[Gankra]

Calling this sufficiently resolved.