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/liballoc/heap.rs

@@ -80,7 +80,7 @@ pub fn usable_size(size: uint, align: uint) -> uint {
 ///
 /// These statistics may be inconsistent if other threads use the allocator
 /// during the call.
-#[unstable(feature = "unnamed_feature")]
+#[unstable(feature = "alloc")]
 pub fn stats_print() {
     imp::stats_print();
 }