Add missing links for CannotReallocInPlace type

Author: GuillaumeGomez

src/libcore/alloc.rs

@@ -359,9 +359,12 @@ impl fmt::Display for AllocErr {
     }
 }
 
-/// The `CannotReallocInPlace` error is used when `grow_in_place` or
-/// `shrink_in_place` were unable to reuse the given memory block for
+/// The `CannotReallocInPlace` error is used when [`grow_in_place`] or
+/// [`shrink_in_place`] were unable to reuse the given memory block for
 /// a requested layout.
+///
+/// [`grow_in_place`]: ./trait.Alloc.html#method.grow_in_place
+/// [`shrink_in_place`]: ./trait.Alloc.html#method.shrink_in_place
 #[unstable(feature = "allocator_api", issue = "32838")]
 #[derive(Clone, PartialEq, Eq, Debug)]
 pub struct CannotReallocInPlace;