Remove send lang item.

It's completely unused.

Author: leoyvens

src/libcore/marker.rs

@@ -39,7 +39,7 @@ use hash::Hasher;
 /// [arc]: ../../std/sync/struct.Arc.html
 /// [ub]: ../../reference/behavior-considered-undefined.html
 #[stable(feature = "rust1", since = "1.0.0")]
-#[lang = "send"]
+#[cfg_attr(stage0, lang = "send")]
 #[rustc_on_unimplemented = "`{Self}` cannot be sent between threads safely"]
 pub unsafe trait Send {
     // empty.

src/librustc/middle/lang_items.rs

@@ -228,7 +228,6 @@ language_item_table! {
     F32ImplItem,                     "f32",                     f32_impl;
     F64ImplItem,                     "f64",                     f64_impl;
 
-    SendTraitLangItem,               "send",                    send_trait;
     SizedTraitLangItem,              "sized",                   sized_trait;
     UnsizeTraitLangItem,             "unsize",                  unsize_trait;
     CopyTraitLangItem,               "copy",                    copy_trait;