Box.setChildPacking

void setChildPacking(gtk.widget.Widget child, bool expand, bool fill, uint padding, gtk.types.PackType packType)

Sets the way child is packed into box.

`child`	the #GtkWidget of the child to set
`expand`	the new value of the expand child property
`fill`	the new value of the fill child property
`padding`	the new value of the padding child property
`packType`	the new value of the pack-type child property