Fix small issues concerning namespacing in test-all suite

* Fix temporary methods on Object leaking across test cases.
* Remove temporary classes/modules leaking across test cases.

test/-ext-/iseq_load/test_iseq_load.rb

@@ -123,6 +123,8 @@ def test_break_ensure_def_method
     assert_equal false, test_break_ensure_def_method
     omit "failing due to exception entry sp mismatch"
     assert_iseq_roundtrip(src)
+  ensure
+    Object.undef_method(:test_break_ensure_def_method) rescue nil
   end
 
   def test_kwarg

test/ruby/test_eval.rb

@@ -488,6 +488,9 @@ def test_define_method_toplevel
       end
     end
     assert_equal(feature6609, feature6609_method)
+  ensure
+    Object.undef_method(:feature6609_block) rescue nil
+    Object.undef_method(:feature6609_method) rescue nil
   end
 
   def test_eval_using_integer_as_binding

test/ruby/test_iseq.rb

@@ -637,6 +637,8 @@ def self.foo
     }
 
     lines
+  ensure
+    Object.send(:remove_const, :A) rescue nil
   end
 
   def test_to_binary_line_tracepoint

test/ruby/test_module.rb

@@ -1728,6 +1728,8 @@ def test_nonascii_name
     assert_equal("TestModule::C\u{df}", c.name, '[ruby-core:24600]')
     c = Module.new.module_eval("class X\u{df} < Module; self; end")
     assert_match(/::X\u{df}:/, c.new.to_s)
+  ensure
+    Object.send(:remove_const, "C\u{df}")
   end
 
 

test/ruby/test_require.rb

@@ -210,6 +210,7 @@ def assert_syntax_error_backtrace
       assert_not_nil(bt = e.backtrace, "no backtrace")
       assert_not_empty(bt.find_all {|b| b.start_with? __FILE__}, proc {bt.inspect})
     end
+  ensure
     $LOADED_FEATURES.replace loaded_features
   end