Free and remove the gadget from the display (and free its gadgetlist if the gadget was a container).
#Gadget The gadget to free. If #PB_All is specified, all the remaining gadgets are freed.
A gadget is freed automatically if one of the following happens:
- The window that contains the gadget is closed.
- The parent of the gadget (ContainerGadget(), PanelGadget() etc.) is freed.
- The program ends.