Optimize ObjectLike::to_string for tables and userdata

Author: khvzak

src/table.rs

@@ -941,7 +941,7 @@ impl ObjectLike for Table {
 
     #[inline]
     fn to_string(&self) -> Result<StdString> {
-        Value::Table(self.clone()).to_string()
+        Value::Table(Table(self.0.copy())).to_string()
     }
 }
 

src/userdata/object.rs

@@ -88,6 +88,6 @@ impl ObjectLike for AnyUserData {
 
     #[inline]
     fn to_string(&self) -> Result<StdString> {
-        Value::UserData(self.clone()).to_string()
+        Value::UserData(AnyUserData(self.0.copy(), self.1)).to_string()
     }
 }