The following gems still used win32api.rb.
hsbt@aluminium:~$ gem-codesearch "require \"win32api\""
/srv/gems/rinderon-0.0.0.1/lib/rinderon/window.rb:require "win32api"
hsbt@aluminium:~$ gem-codesearch "require 'win32api'"
/srv/gems/audio_player-1.0.2/lib/audio_player.rb:require 'win32api'
/srv/gems/easy_io-0.4.2/lib/easy_io.rb:  require 'win32api'
/srv/gems/external_api-1.0.3/lib/external_api.rb:require 'win32api'
/srv/gems/gap50-0.1.1/lib/gap50/preload.rb:    require 'win32api'
/srv/gems/green_shoes-1.1.374/lib/plugins/video.rb:      require 'win32api'
/srv/gems/iegrip-0.1.7/lib/iegrip.rb:require 'win32api'
/srv/gems/mini_term-0.1.3/lib/mini_term/windows.rb:  require 'win32api'
/srv/gems/reline-0.1.5/lib/reline/windows.rb:    require 'win32api'
/srv/gems/rubyinstaller-build-0.1.0/resources/files/reline/windows.rb:    require 'win32api'
/srv/gems/u3d-1.2.3/lib/u3d/utils.rb:        require 'win32api'
/srv/gems/ua-0.0.2/test/test5.rb:require 'win32api'
/srv/gems/undll32-0.3.3/README.md:Notice: it uses `require 'win32api'`, which may not work on your Linux or MacOS systems.