SCUMM: SE: Add 32bit mode for special editions

Note: the updatePalette() call in ScummEngine::scummLoop() has been moved to
ensure that the palette is set when writeRoomColor is called.
SCUMM: SE: add a runtime game flag to switch to classic mode
SCUMM: SE: Resource Manager to read .xml files
SCUMM: SE: DirectDraw Surface and DXT decoder
SCUMM: SE: Allow to downscale
SCUMM: SE: Read unpacked files too
SCUMM: SE: Room rendering WIP