wined3d: Properly handle backbuffer_width/_height=0 in wined3d_device_reset.

[Henri Verbeet]

Is this really the correct behaviour when windowed is FALSE and the
backbuffer width / height is 0? That may just not be allowed at all,
but it seems weird to use the window's dimensions in that case,
instead of e.g. the current display mode.

>     if (!swapchain_desc->backbuffer_width || !swapchain_desc->backbuffer_height
>         || swapchain_desc->backbuffer_width != swapchain->desc.backbuffer_width
>         || swapchain_desc->backbuffer_height != swapchain->desc.backbuffer_height)
Double indent for line continuations, please.

>         window = swapchain_desc->device_window ?
>             swapchain_desc->device_window : device->create_parms.focus_window;
This is really just the same as "window = swapchain->device_window;".

>         if(swapchain_desc->backbuffer_width)
Space between control statements and '('.