Update to libc 0.2.30 for emscripten support

[lilianmoraru]

No description provided.

[lilianmoraru]

For some reason fails at this assert:

fs2-rs/src/lib.rs

Line 325 in 82639f3

assert!(available_space <= free_space);

Curious if it is a test stability problem or in some version of libc something changed(I observed that the tests that passed use an old version of libc, so other versions might of changed the situation too).

[lilianmoraru]

Probably flaky? It ran ok in my case: https://travis-ci.org/lilianmoraru/fs2-rs/builds/268981651

[lilianmoraru]

Side note, the failing test ran on precise, while my run was on the newer trusty.

[danburkert]

Yep looks like a flake. Thanks for the PR! I imagine I should wait till resolution of #19 before cutting a release, right? AFAIK just this change alone isn't worth releasing, since cargo update in downstream apps should have the same effect.

[lilianmoraru]

@danburkert Yes, rust-lang/rust#44116 + #19 need to land first...