[NbtkWidget] add missing forward declaration for nbtk_widget_get_border
[NbtkWidget] add missing forward declaration for nbtk_widget_get_border

jonnylamb/mx,jonnylamb/mx,clutter-project/mx,clutter-project/mx,jonnylamb/mx,jonnylamb/mx,pwithnall/mx,pwithnall/mx,pwithnall/mx,clutter-project/mx,pwithnall/mx,clutter-project/mx