[Feature]: Slide-y bit that goes back on some pistols when empty

[Flaborized]

On some semi-automatic pistols, the slide bit locks back when there's no bullets left in it. This patch adds that to the silenced .22, 9mm pistol and the clock. It always bugged me that this didn't happen, it's kind of a cool visual indicator of a gun being empty and makes them feel a little bit more like a "real thing".

Compare link: https://github.com/goonstation/goonstati...:gunslides

DMI with icons: 
  gun.dmi (Size: 758 bytes / Downloads: 2) , with sprites to be added to icons/obj/guns.dmi

looks like this in-game:

[mbc]

merged