For compatibility, just keep deriving Default for all opaque types

Author: GKFX

bindgen-tests/tests/expectations/tests/libclang-9/issue-544-stylo-creduce-2.rs

@@ -5448,16 +5448,9 @@ pub(crate) mod utils {
         let ty = quote! {
             /// If Bindgen could only determine the size and alignment of a
             /// type, it is represented like this.
-            #[derive(PartialEq, Copy, Clone, Hash, Debug)]
+            #[derive(PartialEq, Copy, Clone, Debug, Default, Hash)]
             #[repr(C)]
             pub struct __BindgenOpaqueArray<T, const N: usize>(pub [T; N]);
-            /// `Default` is only implemented for zero-sized opaque types, since
-            /// Bindgen does not know what contents make sense as a default.
-            impl<T> Default for __BindgenOpaqueArray<T, 0> {
-                fn default() -> Self {
-                    Self([])
-                }
-            }
         };
 
         result.insert(0, ty);

bindgen-tests/tests/expectations/tests/non-type-params.rs

@@ -582,7 +582,7 @@ pub(crate) enum TypeKind {
     /// A compound type, that is, a class, struct, or union.
     Comp(CompInfo),
 
-    /// An opaque type that we just don't understand. All usage of this shoulf
+    /// An opaque type that we just don't understand. All usage of this should
     /// result in an opaque blob of bytes generated from the containing type's
     /// layout.
     Opaque,