Allow chaining of comparisons

Namely for all comparison operators they should be allowed to be chained. The easy way of disambiguating them is since they are all binary operators just chain them with &&. Lastly, this can help with code clearness since the following can be avoided

let x = fn_long();
let y = fn_other();

if 5 < x && x < 10 && y <= x && 5 < y {
    ...
}

and replaced with:

if 5 < fn_other() <= fn_long() < 10 {
}

where the return values of any non_constant is held in reserve so that the function isn't called multiple times.

Start with the issue body and evaluate the proposed comparison-chaining syntax, including the stated && interpretation and reserved return values for non-constant expressions. No files or tests are named; completion would require an agreed design for the Rust language change rather than a localized edit.