Remove unused str_eq lang item

It's not a lang item anymore. Also remove outdated note.

Author: leoyvens

src/libcore/str/mod.rs

@@ -1400,9 +1400,6 @@ Section: Comparing strings
 */
 
 /// Bytewise slice equality
-/// NOTE: This function is (ab)used in rustc::middle::trans::_match
-/// to compare &[u8] byte slices that are not necessarily valid UTF-8.
-#[lang = "str_eq"]
 #[inline]
 fn eq_slice(a: &str, b: &str) -> bool {
     a.as_bytes() == b.as_bytes()

src/librustc/middle/lang_items.rs

@@ -281,8 +281,6 @@ language_item_table! {
     EqTraitLangItem,                 "eq",                      eq_trait;
     OrdTraitLangItem,                "ord",                     ord_trait;
 
-    StrEqFnLangItem,                 "str_eq",                  str_eq_fn;
-
     // A number of panic-related lang items. The `panic` item corresponds to
     // divide-by-zero and various panic cases with `match`. The
     // `panic_bounds_check` item is for indexing arrays.