[poppler] Read some more info from the Font Descriptor

[Kristian Høgsberg]

Albert Astals Cid wrote:
> Hi this patch reads font family, font weifght and font stretch from font 
> descriptor if they are available. That will help querying fontconfig about 
> the font.

This looks good, and should be a good basis for doing good font 
matching.  I think it makes more sense to represent strecth and weight 
as just integers, though.  We're going to use these values with 
fontconfig for building a FcPattern, and fontconfig represents these 
properties as integers so I think it makes sense to make it easy to work 
with fontconfig.

thanks,
Kristian