Merge pull request #4450 from shuujii/move-Kernel-instance_exec-to-BasicObject

Move `Kernel#instance_exec` to `BasicObject`

mrbgems/mruby-object-ext/src/object.c

@@ -120,7 +120,7 @@ mrb_mruby_object_ext_gem_init(mrb_state* mrb)
   mrb_define_method(mrb, n, "to_i", nil_to_i,       MRB_ARGS_NONE());
   mrb_define_module_function(mrb, mrb->kernel_module, "itself", mrb_f_itself, MRB_ARGS_NONE());
 
-  mrb_define_method(mrb, mrb->kernel_module, "instance_exec", mrb_obj_instance_exec, MRB_ARGS_ANY() | MRB_ARGS_BLOCK());
+  mrb_define_method(mrb, mrb_class_get(mrb, "BasicObject"), "instance_exec", mrb_obj_instance_exec, MRB_ARGS_ANY() | MRB_ARGS_BLOCK());
 }
 
 void