Update to new opaque syntax

generator/vulkan/parse.zig

@@ -152,7 +152,7 @@ fn parseBaseType(allocator: *Allocator, ty: *xml.Element) !registry.Declaration
         // macros, which is why this part is not built into the xml/c parser.
         return registry.Declaration{
             .name = name,
-            .decl_type = .{.opaque = {}},
+            .decl_type = .{.external = {}},
         };
     }
 }