Auto merge of #381 - fiveop:fix_musl, r=utkarshkukreti

musl target needs std::mem now

Closes #325.

Author: homu

src/ucontext.rs

@@ -1,7 +1,6 @@
 use libc;
 #[cfg(not(target_env = "musl"))]
 use {Errno, Result};
-#[cfg(not(target_env = "musl"))]
 use std::mem;
 use sys::signal::SigSet;