Rollup of 4 pull requests#64281

Merged

bors merged 8 commits intorust-lang:masterfrom

Centril:rollup-inyqjf8

Sep 8, 2019

Commits on Sep 4, 2019

Use backtrace formatting from the backtrace crate
cramertj
committed

Commits on Sep 6, 2019

Add Iterator comparison methods that take a comparison function
timvermeulen
committed

Commits on Sep 7, 2019