Fix class name validation in `Struct.new`

Before this patch:

  $ bin/mruby -e 'p Struct.new("A-")'
  #=> Struct::"A-"

After this patch:

  $ bin/mruby -e 'p Struct.new("A-")'
  #=> NameError: identifier A- needs to be constant

1 files changed, 1 insertions, 0 deletions

diff --git a/include/mruby/class.h b/include/mruby/class.h
index a68724538..c79a487b5 100644
--- a/include/mruby/class.h
+++ b/include/mruby/class.h
@@ -88,6 +88,7 @@ MRB_API struct RClass* mrb_class_real(struct RClass* cl);
 mrb_value mrb_instance_new(mrb_state *mrb, mrb_value cv);
 
 void mrb_class_name_class(mrb_state*, struct RClass*, struct RClass*, mrb_sym);
+mrb_bool mrb_const_name_p(mrb_state*, const char*, mrb_int);
 mrb_value mrb_class_find_path(mrb_state*, struct RClass*);
 void mrb_gc_mark_mt(mrb_state*, struct RClass*);
 size_t mrb_gc_mark_mt_size(mrb_state*, struct RClass*);