mruby/mruby — pull request #2599 by SatoshiOdawara (2014-09-29 09:11:43+00:00)
Title: target_class should not be TT_ICLASS in instance_eval(string); ref #1152

when mrb_funcall called instance_eval(string), mrb->c->ci->target_class doesn't modified.

```c
mrb_funcall(mrb, mrb_obj_value(mrb->kernel_module), "instance_eval", 1, "class Foo; end");
// ==> TypeError: # is not a class/module
```

target_class should not be TT_ICLASS. ref #1152