Add #[derive(Debug)] for SliceStack and OwnedStack.

src/owned_stack.rs

@@ -7,6 +7,7 @@ use self::alloc::raw_vec::RawVec;
 use self::alloc::boxed::Box;
 
 /// OwnedStack allocates on heap and owns a non-guarded stack.
+#[derive(Debug)]
 pub struct OwnedStack(Box<[u8]>);
 
 impl OwnedStack {

src/slice_stack.rs

@@ -4,6 +4,7 @@
 
 /// SliceStack holds a non-guarded stack allocated elsewhere and provided as a mutable
 /// slice.
+#[derive(Debug)]
 pub struct SliceStack<'a>(pub &'a mut [u8]);
 
 impl<'a> ::stack::Stack for SliceStack<'a> {