Update libc version required by rustc#56562

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bors merged 1 commit intorust-lang:masterfrom

pnkfelix:issue-55465-update-libc-version

Dec 14, 2018

Commits on Dec 12, 2018

Increase required version for crates.io `libc` to get fix from PR rust-lang/libc#1057.
pnkfelix
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