Encapsulate register_fn_raw parameters into NativeCallContext.

src/packages/fn_basic.rs

@@ -12,4 +12,8 @@ mod fn_ptr_functions {
     pub fn name(f: &mut FnPtr) -> ImmutableString {
         f.get_fn_name().clone()
     }
+    #[rhai_fn(name = "is_anonymous", get = "is_anonymous")]
+    pub fn is_anonymous(f: &mut FnPtr) -> bool {
+        f.is_anonymous()
+    }
 }