Trying to fix for i686-apple

Error was "bad pthread_cancel function pointer: rust: 8362822 (0x7f9b46) != c 8358779 (0x7f8b7b)"

Author: oherrala

src/unix/bsd/mod.rs

@@ -491,6 +491,8 @@ extern {
                            oldset: *mut sigset_t) -> ::c_int;
     pub fn sem_open(name: *const ::c_char, oflag: ::c_int, ...) -> *mut sem_t;
     pub fn getgrnam(name: *const ::c_char) -> *mut ::group;
+    #[cfg_attr(all(target_os = "macos", target_arch = "x86"),
+               link_name = "pthread_cancel$UNIX2003")]
     pub fn pthread_cancel(thread: ::pthread_t) -> ::c_int;
     pub fn pthread_kill(thread: ::pthread_t, sig: ::c_int) -> ::c_int;
     pub fn sem_unlink(name: *const ::c_char) -> ::c_int;