[DDRAW] Mute aggressive log-spam in game 'Anno 1602' and 'Diablo II demo'

*Reproduction steps*

• 0.4.15-dev-5068-g7512522 gcc8.4.0 dbg RosBEWin2.2.1
• on VBox 4.3.12 + VBox 3d accelerated graphics driver installed in safe mode
• switch the bpp to 16bit before starting the game to workaround it not starting (with 32bpp)

With that the game Anno 1602 finally runs very well and renders the game with excellent palette even.

Still

fixme:(dll/directx/wine/ddraw/utils.c:584) Unhandled flags 0x20.

gets logged many times per second.

Affects also other apps/games that use DDraw with the VBox 3d accelerated display driver (iirc Diablo II does that too).
The task aims to mute that logging to improve the performance a bit.

See 0.4.15-dev-5068-g7512522_Anno1602_LogSpam.log.
It floods most of the log during the whole runtime of the game.

I will open a PR in a minute.