merge unused-extern-crate and unnecessary-extern-crate lints#51015

Merged

bors merged 3 commits intorust-lang:masterfrom

nikomatsakis:issue-50672-remove-extern-crate-idiom

Jun 2, 2018

Commits on Jun 1, 2018

extend `unused_extern_crates` lint with a suggestion to remove
nikomatsakis
committed
merge UNNECESSARY_EXTERN_CRATE and UNUSED_EXTERN_CRATES
nikomatsakis
committed
rework to report errors from crates in a consistent order
nikomatsakis
committed