Remove deprecated heap modules

The heap.rs file was already unused.

src/libstd/collections/mod.rs

@@ -438,7 +438,7 @@ pub use self::hash_map::HashMap;
 pub use self::hash_set::HashSet;
 
 #[unstable(feature = "try_reserve", reason = "new API", issue="48043")]
-pub use heap::CollectionAllocErr;
+pub use alloc::CollectionAllocErr;
 
 mod hash;
 

src/libstd/error.rs

@@ -23,13 +23,13 @@
 // coherence challenge (e.g., specialization, neg impls, etc) we can
 // reconsider what crate these items belong in.
 
+use alloc::{AllocErr, LayoutErr, CannotReallocInPlace};
 use any::TypeId;
 use borrow::Cow;
 use cell;
 use char;
 use core::array;
 use fmt::{self, Debug, Display};
-use heap::{AllocErr, LayoutErr, CannotReallocInPlace};
 use mem::transmute;
 use num;
 use str;

src/libstd/lib.rs

@@ -499,13 +499,6 @@ pub mod process;
 pub mod sync;
 pub mod time;
 
-#[unstable(feature = "allocator_api", issue = "32838")]
-#[rustc_deprecated(since = "1.27.0", reason = "module renamed to `alloc`")]
-/// Use the `alloc` module instead.
-pub mod heap {
-    pub use alloc::*;
-}
-
 // Platform-abstraction modules
 #[macro_use]
 mod sys_common;