wined3d: Set the WINED3DPBLENDCAPS_SRCALPHASAT destination blend cap when ARB_blend_func_extended is supported.

It appears that particularly on slower setups, on occasion we don't receive
WM_DISPLAYCHANGE messages after a mode change. The theory is that the
SendMessageTimeoutW() call in X11DRV_resize_desktop() ends up hitting the
is_queue_hung() check in the send_message handler in the server, and the
PeekMessage() calls should avoid that.