[tests] Fix GdkPixbuf declaration for non-installed GDK+ headers
[tests] Fix GdkPixbuf declaration for non-installed GDK+ headers

Pecisk/libgdata-gtasks,pwithnall/libgdata,Pecisk/libgdata-gtasks,Pecisk/libgdata,Pecisk/libgdata,Distrotech/libgdata,Distrotech/libgdata,pwithnall/libgdata,GNOME/libgdata,Pecisk/libgdata,Distrotech/libgdata,Pecisk/libgdata-gtasks