[ruby/win32ole] Move toplevel constant for olegen under `WIN32OLE`

https://github.com/ruby/win32ole/commit/78ff137c0f

ext/win32ole/lib/win32ole/property.rb

@@ -1,7 +1,12 @@
 # frozen_string_literal: false
-# OLEProperty
-# helper class of Property with arguments.
-class OLEProperty
+
+class WIN32OLE
+end
+
+# OLEProperty is a helper class of Property with arguments, used by
+# `olegen.rb`-generated files.
+class WIN32OLE::Property
+  # :stopdoc:
   def initialize(obj, dispid, gettypes, settypes)
     @obj = obj
     @dispid = dispid
@@ -14,4 +19,11 @@ class OLEProperty
   def []=(*args)
     @obj._setproperty(@dispid, args, @settypes)
   end
+  # :stopdoc:
+end
+
+module WIN32OLE::VariantType
+  # Alias for `olegen.rb`-generated files, that should include
+  # WIN32OLE::VARIANT.
+  OLEProperty = WIN32OLE::Property
 end