Kickback pic

kickback_pic determines which animation frame the player's current weapon is in.

The difference between this struct member and the gamevar weaponcount is that updates to this struct member will be propagated back to the hardcoded behavior, while updates to weaponcount will not.

Each tic, the executable copies the value from this member to weaponcount, i.e. "getplayer[THISACTOR].kickback_pic weaponcount".

If kickback_pic is set to 1, then it will continue to increment and cause the currently selected weapon to fire, returning to 0 when the weapon reaches its total firing time.