Merge pull request #2634 from xxuejie/fix-mrb-iv-check-prototype

Fix mrb_iv_check function decleration

include/mruby/variable.h

@@ -40,7 +40,7 @@ MRB_API mrb_bool mrb_const_defined(mrb_state*, mrb_value, mrb_sym);
 MRB_API void mrb_const_remove(mrb_state*, mrb_value, mrb_sym);
 
 MRB_API mrb_bool mrb_iv_p(mrb_state *mrb, mrb_sym sym);
-MRB_API mrb_bool mrb_iv_check(mrb_state *mrb, mrb_sym sym);
+MRB_API void mrb_iv_check(mrb_state *mrb, mrb_sym sym);
 MRB_API mrb_value mrb_obj_iv_get(mrb_state *mrb, struct RObject *obj, mrb_sym sym);
 MRB_API void mrb_obj_iv_set(mrb_state *mrb, struct RObject *obj, mrb_sym sym, mrb_value v);
 MRB_API mrb_bool mrb_obj_iv_defined(mrb_state *mrb, struct RObject *obj, mrb_sym sym);