Get the child of the Grid at the given position

Property definitions

gtk $ GtkGrid :: get_child_at
	# Get the child of the Grid at the given position
	fun get_child_at(left: Int, top: Int): GtkWidget `{
		return gtk_grid_get_child_at(self, left, top);
	`}
lib/gtk/v3_4/gtk_core.nit:378,2--381,3