Add <*const T>::align_offset and use it in memchr

src/libstd/lib.rs

@@ -242,6 +242,7 @@
 #![feature(allocator_internals)]
 #![feature(allow_internal_unsafe)]
 #![feature(allow_internal_unstable)]
+#![feature(align_offset)]
 #![feature(asm)]
 #![feature(box_syntax)]
 #![feature(cfg_target_has_atomic)]