Remove parent namespace from Readline test classes

The namespace "Readline" doesn't exist when running tests if readline.so
doesn't exist and Reline exists. So test classes shouldn't be at nested
namespaces under "Readline".

test/readline/test_readline_history.rb

@@ -2,7 +2,7 @@
 require_relative "helper"
 require "test/unit"
 
-module Readline::BasetestHistory
+module BasetestReadlineHistory
   def setup
     Readline::HISTORY.clear
   end
@@ -252,8 +252,8 @@ module Readline::BasetestHistory
   end
 end
 
-class Readline::TestHistory < Test::Unit::TestCase
-  include Readline::BasetestHistory
+class TestReadlineHistory < Test::Unit::TestCase
+  include BasetestReadlineHistory
 
   def setup
     use_ext_readline
@@ -268,8 +268,8 @@ end if defined?(::ReadlineSo) && defined?(::ReadlineSo::HISTORY) &&
    end
    )
 
-class Reline::TestHistory < Test::Unit::TestCase
-  include Readline::BasetestHistory
+class TestRelineAsReadlineHistory < Test::Unit::TestCase
+  include BasetestReadlineHistory
 
   def setup
     use_lib_reline