Compile error on Windows

[Jeff Mitchell]

Andre Canrinus wrote:
> I'm trying to build the latest source on Windows/Vista.
> 
> The build process stopped on compiling ProgressSlider.cpp
> 
> I found a typo on line 69
> 
> #endif,
> 
> The reailing comma ',' causes my compiler (msvc) not to parse this line
> correctly.

Fixed.  Thanks!