Enable #[ffi_const]

safe_libc/src/errno.rs

@@ -7,7 +7,7 @@ use core::fmt;
 pub struct Errno(pub libc::c_int);
 
 extern "C" {
-	//#[ffi_const]
+	#[ffi_const]
 	pub fn __errno_location() -> *mut libc::c_int;
 }
 

safe_libc/src/lib.rs

@@ -1,7 +1,7 @@
 #![no_std]
 #![feature(extern_types)]
 #![feature(slice_ptr_len)]
-// #![feature(ffi_const)]
+#![feature(ffi_const)]
 
 extern crate alloc;