commctrl: modularize progress drawing

[Felix Nawothnig]

Dimi Paun wrote:
> It has become the norm lately to not have the ALLCAPS_ prefix
> for internal static functions, but rather have names_with_underscores
> to easily tell them apart from Win32 APIs.
> 
> So for the above, I guess get_led_size() would be preferable.

I thought the only half-official rule would be to keep the style 
consistent with the rest of the file, which is just what Frank is doing 
here since progress.c uses ALLCAPS_CamelCase everywhere?

And actually I'd prefer ALLCAPS_CamcelCase over kernel_style since the 
latter looks quite alien in Win32 code... and looking at wine-patches 
from the last weeks it seems I'm not alone. :)

Felix