Add with_iterator to TypeBuilder.

tests/build_type.rs

@@ -45,11 +45,21 @@ fn build_type() -> Result<(), Box<EvalAltResult>> {
         }
     }
 
+    impl IntoIterator for Vec3 {
+        type Item = INT;
+        type IntoIter = std::vec::IntoIter<Self::Item>;
+
+        fn into_iter(self) -> Self::IntoIter {
+            vec![self.x, self.y, self.z].into_iter()
+        }
+    }
+
     impl CustomType for Vec3 {
         fn build(mut builder: TypeBuilder<Self>) {
             builder
                 .with_name("Vec3")
                 .with_fn("vec3", Self::new)
+                .with_iterator()
                 .with_get_set("x", Self::get_x, Self::set_x)
                 .with_get_set("y", Self::get_y, Self::set_y)
                 .with_get_set("z", Self::get_z, Self::set_z);