Trackbar size fixes

[Duane Clark]

BiGgUn wrote:
>>As BiGgUn suggests, in TRACKBAR_InitializeThumb, setting:
>>     infoPtr->uThumbLen = 21;
> 
> 
> In this case 21 is a magic number. In fact, infoPtr->uThumbLen equals SM_CYCAPTION.
> 

 From the Wine include file:

winuser.h:#define SM_CYCAPTION         4

So I don't think we want to use that value.