wined3d: Check if we can do the blit before messing with surface flags in IWineD3DSurfaceImpl_BltOverride().

As an added benefit blit_supported() will now get the rectangles in the
correct coordinate system.

Caused by commit 776a8662. Fixes parse
failures for BSTR's where encoding is explicitly UTF-16.

Translation by Đorđe Vasiljević.

Translation by Đorđe Vasiljević.

Translation by Đorđe Vasiljević.

Translation by Đorđe Vasiljević.