font families in Pango::FontDescription

[Rob Benton <rob benton conwaycorp net>]

When you create a FontDescription is there a priority in the list of 
font families you specify?  I'm noticing that:

Pango::FontDescription fontdesc("sans, monospace, courier new, bold 12");

always seems to select 'courier new' as the font no matter what order I 
put them in.  If I remove courier new from the list then the first font 
specified is the one used.