opt-in to feature for accessing std::mem::POST_DROP_USIZE.

Author: pnkfelix

src/liballoc/lib.rs

@@ -74,7 +74,7 @@
 #![feature(box_syntax)]
 #![feature(optin_builtin_traits)]
 #![feature(unboxed_closures)]
-#![feature(unsafe_no_drop_flag)]
+#![feature(unsafe_no_drop_flag, filling_drop)]
 #![feature(core)]
 #![feature(unique)]
 #![cfg_attr(test, feature(test, alloc, rustc_private))]

src/libcollections/lib.rs

@@ -33,7 +33,7 @@
 #![feature(unicode)]
 #![feature(unsafe_destructor)]
 #![feature(unique)]
-#![feature(unsafe_no_drop_flag)]
+#![feature(unsafe_no_drop_flag, filling_drop)]
 #![feature(step_by)]
 #![feature(str_char)]
 #![cfg_attr(test, feature(rand, rustc_private, test))]