Improve performance of spsc_queue and stream.

This commit makes two main changes.
1. It switches the spsc_queue node caching strategy from keeping a shared
counter of the number of nodes in the cache to keeping a consumer only counter
of the number of node eligible to be cached.
2. It separate the consumer and producers fields of spsc_queue and stream into
a producer cache line and consumer cache line.

src/libstd/lib.rs

@@ -244,6 +244,7 @@
 #![feature(allow_internal_unstable)]
 #![feature(align_offset)]
 #![feature(asm)]
+#![feature(attr_literals)]
 #![feature(box_syntax)]
 #![feature(cfg_target_has_atomic)]
 #![feature(cfg_target_thread_local)]
@@ -290,6 +291,7 @@
 #![feature(prelude_import)]
 #![feature(rand)]
 #![feature(raw)]
+#![feature(repr_align)]
 #![feature(repr_simd)]
 #![feature(rustc_attrs)]
 #![cfg_attr(not(stage0), feature(rustc_const_unstable))]