Rollup of 10 pull requests#50847

Merged

bors merged 26 commits intorust-lang:masterfrom

Mark-Simulacrum:rollup

May 18, 2018

Commits on May 2, 2018

Remove leftover tab in libtest outputs
phansch
committed

Commits on May 10, 2018

Improve format string errors
estebank
committed

Commits on May 11, 2018

Tweak `nearest_common_ancestor()`.
nnethercote
committed

Commits on May 15, 2018

Add Option::xor method
Clar Charr
committed

Commits on May 16, 2018

Commits on May 17, 2018