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/rustbook/main.rs

@@ -9,7 +9,13 @@
 // except according to those terms.
 
 #![feature(slicing_syntax, box_syntax)]
-#![feature(unnamed_feature)]
+#![feature(collections)]
+#![feature(core)]
+#![feature(io)]
+#![feature(os)]
+#![feature(path)]
+#![feature(rustc_private)]
+#![feature(rustdoc)]
 
 extern crate regex;