Merge ref '1be6b13be73d' from rust-lang/rust

Pull recent changes from https://github.com/rust-lang/rust via Josh.

Upstream ref: 1be6b13be73dc12e98e51b403add4c41a0b77759
Filtered ref: ec48142
Upstream diff: rust-lang/rust@caccb4d...1be6b13

This merge was created using https://github.com/rust-lang/josh-sync.

Author: The rustc-josh-sync Cronjob Bot

compiler-builtins/src/lib.rs

@@ -7,7 +7,6 @@
 #![feature(compiler_builtins)]
 #![feature(core_intrinsics)]
 #![feature(linkage)]
-#![feature(asm_cfg)]
 #![feature(naked_functions)]
 #![feature(repr_simd)]
 #![feature(macro_metavar_expr_concat)]