Set unstable feature names appropriately

* `core` - for the core crate
* `hash` - hashing
* `io` - io
* `path` - path
* `alloc` - alloc crate
* `rand` - rand crate
* `collections` - collections crate
* `std_misc` - other parts of std
* `test` - test crate
* `rustc_private` - everything else

src/test/compile-fail/lint-uppercase-variables.rs

@@ -12,7 +12,8 @@
 
 #![allow(dead_code)]
 #![deny(non_snake_case)]
-#![feature(unnamed_feature)]
+#![feature(path)]
+#![feature(io)]
 
 use std::io::File;
 use std::io::IoError;