Auto merge of #1133 - glandium:musl-mips, r=gnzlbg
Auto merge of #1133 - glandium:musl-mips, r=gnzlbg

Add missing condition for musl mips64

unix::uclibc::mips has both support for mips and mips64, but it's
currently only imported for mips.

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