[3/5] wined3d: Make the offscreen render mode a registry setting

[Ivan Gyurdiev]

Ivan Gyurdiev wrote:
> This flag needs to be per adapter - should be added to device.c like 
> the shader mode.
I meant the device structure.

Also, the mode selection should include configuration and support 
detection - I think you're missing the support detection. Imho there 
should be a select_offscreen_mode() function like the shader mode is 
done, selecting between fbo, pbuffer, and none.