Remove unused feature gates from cg_ssa and cg_utils

Author: bjorn3

src/librustc_codegen_ssa/lib.rs

@@ -1,10 +1,6 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
 #![feature(bool_to_option)]
 #![feature(box_patterns)]
-#![feature(box_syntax)]
-#![feature(core_intrinsics)]
-#![feature(libc)]
-#![feature(stmt_expr_attributes)]
 #![feature(try_blocks)]
 #![feature(in_band_lifetimes)]
 #![feature(nll)]

src/librustc_codegen_utils/lib.rs

@@ -3,10 +3,6 @@
 //! This API is completely unstable and subject to change.
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![feature(arbitrary_self_types)]
-#![feature(box_patterns)]
-#![feature(box_syntax)]
-#![feature(core_intrinsics)]
 #![feature(never_type)]
 #![feature(nll)]
 #![feature(in_band_lifetimes)]