Remove default Kernel#method_missing.

Internal method_missing works without problems.

src/kernel.c

@@ -969,6 +969,7 @@ mrb_method_missing(mrb_state *mrb, mrb_sym name, mrb_value self, mrb_value args)
  *     r.xxiii   #=> 23
  *     r.mm      #=> 2000
  */
+#ifndef MRB_DEFAULT_METHOD_MISSING
 static mrb_value
 mrb_obj_missing(mrb_state *mrb, mrb_value mod)
 {
@@ -981,6 +982,7 @@ mrb_obj_missing(mrb_state *mrb, mrb_value mod)
   /* not reached */
   return mrb_nil_value();
 }
+#endif
 
 static inline mrb_bool
 basic_obj_respond_to(mrb_state *mrb, mrb_value obj, mrb_sym id, int pub)
@@ -1214,7 +1216,9 @@ mrb_init_kernel(mrb_state *mrb)
   mrb_define_method(mrb, krn, "iterator?",                  mrb_f_block_given_p_m,           MRB_ARGS_NONE());    /* 15.3.1.3.25 */
   mrb_define_method(mrb, krn, "kind_of?",                   mrb_obj_is_kind_of_m,            MRB_ARGS_REQ(1));    /* 15.3.1.3.26 */
   mrb_define_method(mrb, krn, "local_variables",            mrb_local_variables,             MRB_ARGS_NONE());    /* 15.3.1.3.28 */
+#ifndef MRB_DEFAULT_METHOD_MISSING
   mrb_define_method(mrb, krn, "method_missing",             mrb_obj_missing,                 MRB_ARGS_ANY());     /* 15.3.1.3.30 */
+#endif
   mrb_define_method(mrb, krn, "methods",                    mrb_obj_methods_m,               MRB_ARGS_OPT(1));    /* 15.3.1.3.31 */
   mrb_define_method(mrb, krn, "nil?",                       mrb_false,                       MRB_ARGS_NONE());    /* 15.3.1.3.32 */
   mrb_define_method(mrb, krn, "object_id",                  mrb_obj_id_m,                    MRB_ARGS_NONE());    /* 15.3.1.3.33 */

test/t/nomethoderror.rb

@@ -21,37 +21,6 @@ assert('NoMethodError#args', '15.2.32.2.1') do
   end
 end
 
-assert('Can still raise when Kernel#method_missing is removed') do
-  assert_raise(NoMethodError) do
-    begin
-      Kernel.alias_method(:old_method_missing, :method_missing)
-      Kernel.remove_method(:method_missing)
-      1.__send__(:foo)
-    ensure
-      Kernel.alias_method(:method_missing, :old_method_missing)
-      Kernel.remove_method(:old_method_missing)
-    end
-  end
-end
-
-assert('Can still call super when Kernel#method_missing is removed') do
-  assert_raise(NoMethodError) do
-    class A
-      def foo
-        super
-      end
-    end
-    begin
-      Kernel.alias_method(:old_method_missing, :method_missing)
-      Kernel.remove_method(:method_missing)
-      A.new.foo
-    ensure
-      Kernel.alias_method(:method_missing, :old_method_missing)
-      Kernel.remove_method(:old_method_missing)
-    end
-  end
-end
-
 assert("NoMethodError#new does not return an exception") do
   begin
     class << NoMethodError