Remove Rc wrapping of BuiltinFnPtr in BuiltinFn wrapper

I'm trying to remember why this was added in the first place - I think
to simplifly cloning? It's not important now though.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

src/object.rs

@@ -86,7 +86,7 @@ pub enum BuiltinExit {
 #[derive(Clone, Finalize)]
 pub struct BuiltinFn {
     name: Rc<String>,
-    fun: Rc<BuiltinFnPtr>,
+    fun: BuiltinFnPtr,
 }
 
 unsafe impl Trace for BuiltinFn {
@@ -100,7 +100,7 @@ impl PartialEq for BuiltinFn {
 }
 
 impl BuiltinFn {
-    pub fn new(name: String, fun: Rc<BuiltinFnPtr>) -> Self {
+    pub fn new(name: String, fun: BuiltinFnPtr) -> Self {
         BuiltinFn {
             name: Rc::new(name),
             fun,
@@ -184,7 +184,7 @@ macro_rules! vtable {
 
 macro_rules! builtin_fn {
     ($name:expr, $fun:expr) => {{
-        BuiltinFnObj::new(BuiltinFn::new($name.to_string(), Rc::new($fun))).into_gc()
+        BuiltinFnObj::new(BuiltinFn::new($name.to_string(), $fun)).into_gc()
     }};
 }
 

src/vm/machine.rs

@@ -332,7 +332,7 @@ impl MachineBuilder {
     ) {
         self.register_global(
             name,
-            BuiltinFnObj::new(BuiltinFn::new(name.to_string(), Rc::new(fun))).into_gc(),
+            BuiltinFnObj::new(BuiltinFn::new(name.to_string(), fun)).into_gc(),
         );
     }