Make TagsIter and ModuleIter Copy and Clone

src/header.rs

@@ -6,7 +6,7 @@ pub struct Tag {
     // tag specific fields
 }
 
-#[derive(Debug)]
+#[derive(Copy, Clone, Debug)]
 pub struct TagIter {
     pub current: *const Tag,
 }

src/module.rs

@@ -36,7 +36,7 @@ pub fn module_iter(iter: TagIter) -> ModuleIter {
     ModuleIter { iter: iter }
 }
 
-#[derive(Debug)]
+#[derive(Copy, Clone, Debug)]
 pub struct ModuleIter {
     iter: TagIter,
 }