CGE2: Fix graphic glitch at closing the game.
CGE2: Get rid of _flag.
CGE2: Don't bother with  saving/loading sound options.

We always get them for the setting of the Launcher.
CGE2: Implement snFlash().
CGE2: Remove not useful comment from switchScene().
CGE2: Get rid of kCrackedText.
CGE2: Get rid of kExitOkText.
CGE2: Remove unused code.
CGE2: Implement snCycle, add stub for Vga::rotate().
CGE2: Initialize Vga::_rot properly.
CGE2: Implement Vga::rotate().
CGE2: Get rid of sndSetVolume() and connected code.
CGE2: Implement setAutoColors().

Add a redefinition of closest() to do so.
CGE2: Move ColorBank and kColorNum to one place.

They are strongly connected.
CGE2: Remove unnecessary CHECKME comment.
CGE2: Remove unused functions from EncryptedStream.