Remove core::any::AnyPrivate

[Previously](e5da6a7),
the `Any` trait was split into a private portion and an (empty) public
portion, in order to hide the implementation strategy used for
downcasting. However, the [new
rules](e9ad12c)
for privacy forbid `AnyPrivate` from actually being private.

This patch thus reverts the introduction of `AnyPrivate`.

Although this is unlikely to break any real code, it removes a public
trait and is therefore a:

[breaking-change]

src/libcore/any.rs

@@ -91,20 +91,15 @@ pub enum Void { }
 /// Every type with no non-`'static` references implements `Any`, so `Any` can
 /// be used as a trait object to emulate the effects dynamic typing.
 #[stable]
-pub trait Any: AnyPrivate + 'static {}
-
-/// An inner trait to ensure that only this module can call `get_type_id()`.
-pub trait AnyPrivate {
+pub trait Any: 'static {
     /// Get the `TypeId` of `self`
     fn get_type_id(&self) -> TypeId;
 }
 
-impl<T: 'static> AnyPrivate for T {
+impl<T: 'static> Any for T {
     fn get_type_id(&self) -> TypeId { TypeId::of::<T>() }
 }
 
-impl<T: 'static + AnyPrivate> Any for T {}
-
 ///////////////////////////////////////////////////////////////////////////////
 // Extension methods for Any trait objects.
 // Implemented as three extension traits so that the methods can be generic.