Auto merge of #1149 - palfrey:travis-xenial, r=alexcrichton
Auto merge of #1149 - palfrey:travis-xenial, r=alexcrichton

Upgrade Travis to using Xenial environment

One part "lets use the latest things", to several parts "might this fix #1148"

rust-lang-nursery/libc,rust-lang/libc,rust-lang/libc,rust-lang-nursery/libc,rust-lang/libc,rust-lang-nursery/libc