comctl32: Update progress bar only if it moves

[Nikolay Sivov]

On 3/15/2011 00:16, Maarten Lankhorst wrote:
> ---
> Hopefully helps a little with lord of the rings online installer. It 
> seems to be fanatical about updating the position, which may result in 
> too many unnecessary redraws.
Patch is wrong. This is inefficient but it's how native control works, 
it invalidates progress bar no matter what if position is changed. I 
tested so far PBM_DELTAPOS, PBM_SETPOS, PBM_STEPIT.

So this change can break subclass processing for example, when 
application expects WM_PAINT.