New deprecated_suggestion feature, use in tests

Author: jhpratt

core/src/lib.rs

@@ -166,6 +166,7 @@
 #![feature(const_refs_to_cell)]
 #![feature(decl_macro)]
 #![feature(derive_default_enum)]
+#![cfg_attr(not(bootstrap), feature(deprecated_suggestion))]
 #![feature(doc_cfg)]
 #![feature(doc_notable_trait)]
 #![feature(rustdoc_internals)]

std/src/lib.rs

@@ -270,6 +270,7 @@
 #![feature(doc_cfg)]
 #![feature(doc_cfg_hide)]
 #![feature(rustdoc_internals)]
+#![cfg_attr(not(bootstrap), feature(deprecated_suggestion))]
 #![feature(doc_masked)]
 #![feature(doc_notable_trait)]
 #![feature(dropck_eyepatch)]