Add `Kernel#itself`; CRuby2.2

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

@@ -222,6 +222,22 @@ mrb_f_hash(mrb_state *mrb, mrb_value self)
   return tmp;
 }
 
+/*
+ *  call-seq:
+ *     obj.itself -> an_object
+ *
+ *  Returns <i>obj</i>.
+ *
+ *      string = 'my string' #=> "my string"
+ *      string.itself.object_id == string.object_id #=> true
+ *
+ */
+static mrb_value
+mrb_f_itself(mrb_state *mrb, mrb_value self)
+{
+  return self;
+}
+
 void
 mrb_mruby_kernel_ext_gem_init(mrb_state *mrb)
 {
@@ -235,6 +251,7 @@ mrb_mruby_kernel_ext_gem_init(mrb_state *mrb)
   mrb_define_module_function(mrb, krn, "String", mrb_f_string, MRB_ARGS_REQ(1));
   mrb_define_module_function(mrb, krn, "Array", mrb_f_array, MRB_ARGS_REQ(1));
   mrb_define_module_function(mrb, krn, "Hash", mrb_f_hash, MRB_ARGS_REQ(1));
+  mrb_define_module_function(mrb, krn, "itself", mrb_f_itself, MRB_ARGS_NONE());
 }
 
 void