rollup merge of #20315: alexcrichton/std-sync

Conflicts:
	src/libstd/rt/exclusive.rs
	src/libstd/sync/barrier.rs
	src/libstd/sys/unix/pipe.rs
	src/test/bench/shootout-binarytrees.rs
	src/test/bench/shootout-fannkuch-redux.rs

src/libstd/rt/util.rs

@@ -46,7 +46,7 @@ pub fn limit_thread_creation_due_to_osx_and_valgrind() -> bool {
 }
 
 pub fn min_stack() -> uint {
-    static MIN: atomic::AtomicUint = atomic::INIT_ATOMIC_UINT;
+    static MIN: atomic::AtomicUint = atomic::ATOMIC_UINT_INIT;
     match MIN.load(atomic::SeqCst) {
         0 => {}
         n => return n - 1,