Integrate `Fixnum` class into `Integer` class

* The `Fixnum` constant is now an alias for the `Integer` class.
* Remove `struct mrb_state::fixnum_class` member.
  If necessary, use `struct mrb_state::integer_class` instead.

1 files changed, 1 insertions, 1 deletions

diff --git a/test/t/kernel.rb b/test/t/kernel.rb
index 606150147..cab1ddd3d 100644
--- a/test/t/kernel.rb
+++ b/test/t/kernel.rb
@@ -76,7 +76,7 @@ assert('Kernel.raise', '15.3.1.2.12') do
 end
 
 assert('Kernel#__id__', '15.3.1.3.3') do
-  assert_equal Fixnum, __id__.class
+  assert_equal Integer, __id__.class
 end
 
 assert('Kernel#__send__', '15.3.1.3.4') do