SCUMM: Add support for Steam (testapp.exe)
SCUMM: Add support for CDDA.SOU used by the Steam version of Loom
SCUMM: Bypass copyprotection check for Amiga Indy3
GUI: Hide save/load chooser implementation.
BASE: Add operator* to PluginSubclass.
GUI: Refactor engine plugin access out of SaveLoadChooserImpl into SaveLoadChooser.
GUI: Fix include guard of saveload.h.
GUI: Create an interface for save/load dialogs.
GUI: Implement a new load chooser, which displays a list of thumbnails.
GUI: Hook up the new load chooser for > 320x200 and engines which support thumbnails.
GUI: Allow tooltips to be changed after widget creation.
GUI: Show additional meta data in the thumbnail load chooser via tooltip.
GUI: Don't distribute vertical space between buttons in the thumbnail load chooser.
GUI: Fix copy&paste error affecting vertical spacing in thumbnail load chooser.
GUI: Only update save list when the dialog opens in thumbnail load chooser.
GUI: Allow the user to switch between list and thumbnail based load chooser.
GUI: Fix memory leaks in LoadChooserThumbnailed::destroyButtons.

GuiObject::removeWidget only removes the widget from the widget list, but
doesn't delete it. Oops.
GUI: Remember last save/load chooser selection.
GUI: Use a black rect when no thumbnail is available in the thumbnail load chooser.
GUI: Use a slightly bigger vertical spacing in the thumbnail load chooser.