Fix references to Option through dox
diff --git a/src/unix/mod.rs b/src/unix/mod.rs
index 75c1855..8f1d1a0 100644
--- a/src/unix/mod.rs
+++ b/src/unix/mod.rs
@@ -338,7 +338,7 @@
pub fn pthread_detach(thread: ::pthread_t) -> ::c_int;
pub fn sched_yield() -> ::c_int;
pub fn pthread_key_create(key: *mut pthread_key_t,
- dtor: Option<unsafe extern fn(*mut ::c_void)>)
+ dtor: ::dox::Option<unsafe extern fn(*mut ::c_void)>)
-> c_int;
pub fn pthread_key_delete(key: pthread_key_t) -> c_int;
pub fn pthread_getspecific(key: pthread_key_t) -> *mut ::c_void;