Do not propagate collect_garbage flag when clonning Lua

Author: khvzak

src/state.rs

@@ -49,7 +49,6 @@ pub use raw::RawLua;
 use util::{callback_error_ext, StateGuard};
 
 /// Top level Lua struct which represents an instance of Lua VM.
-#[derive(Clone)]
 pub struct Lua {
     pub(self) raw: XRc<ReentrantMutex<RawLua>>,
     // Controls whether garbage collection should be run on drop
@@ -151,6 +150,16 @@ impl Drop for Lua {
     }
 }
 
+impl Clone for Lua {
+    #[inline]
+    fn clone(&self) -> Self {
+        Lua {
+            raw: XRc::clone(&self.raw),
+            collect_garbage: false,
+        }
+    }
+}
+
 impl fmt::Debug for Lua {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "Lua({:p})", self.lock().state())