Remove unused feature gates from librustc

Author: bjorn3

src/librustc/lib.rs

@@ -27,7 +27,6 @@
 //! This API is completely unstable and subject to change.
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![feature(arbitrary_self_types)]
 #![feature(bool_to_option)]
 #![feature(box_patterns)]
 #![feature(box_syntax)]
@@ -39,21 +38,15 @@
 #![feature(overlapping_marker_traits)]
 #![feature(extern_types)]
 #![feature(nll)]
-#![feature(optin_builtin_traits)]
 #![feature(option_expect_none)]
 #![feature(range_is_empty)]
 #![feature(specialization)]
-#![feature(unboxed_closures)]
-#![feature(thread_local)]
-#![feature(trace_macros)]
 #![feature(trusted_len)]
 #![feature(vec_remove_item)]
 #![feature(stmt_expr_attributes)]
-#![feature(integer_atomics)]
 #![feature(test)]
 #![feature(in_band_lifetimes)]
 #![feature(crate_visibility_modifier)]
-#![feature(log_syntax)]
 #![feature(associated_type_bounds)]
 #![feature(rustc_attrs)]
 #![feature(hash_raw_entry)]