Mark dead code.

Author: adetaylor

src/lib.rs

@@ -496,6 +496,7 @@ unsafe impl cxx::ExternType for c_char16_t {
 /// If you come across a method, type or function which refers to this type,
 /// it indicates that autocxx couldn't generate that binding. A documentation
 /// comment should be attached indicating the reason.
+#[allow(dead_code)]
 pub struct BindingGenerationFailure {
     _unallocatable: [*const u8; 0],
     _pinned: core::marker::PhantomData<core::marker::PhantomPinned>,