implement __functor

fix-vm/src/lib.rs

@@ -223,6 +223,8 @@ pub struct Vm<'gc> {
 
     #[collect(require_static)]
     result: Option<Result<fix_common::Value>>,
+
+    functor_sym: StringId,
 }
 
 enum OperandData {
@@ -340,6 +342,8 @@ impl<'gc> Vm<'gc> {
             force_mode,
 
             result: None,
+
+            functor_sym: ctx.intern_string("__functor"),
         }
     }