Remove unused features

examples/intrinsics.rs

@@ -6,10 +6,8 @@
 #![allow(unused_features)]
 #![cfg_attr(thumb, no_main)]
 #![deny(dead_code)]
-#![feature(alloc_system)]
 #![feature(asm)]
 #![feature(compiler_builtins_lib)]
-#![feature(core_float)]
 #![feature(lang_items)]
 #![feature(start)]
 #![feature(allocator_api)]