- Fixed: ABackpackItem::CreateTossable did not check for failure from the supermethod.
Move C_ExecCmdLineParams() call slightly later in the startup process.

- Fixed: You could not set any CVARINFO-defined cvars from the command line
  because command line console commands were executed before wads were
  even loaded. Off the top of my head, I can't think of anything that would\
  break by having them get executed after wads are loaded.
Do not follow NextThinker links in DestroyThinkersInList

- Fixed: DThinker::Destroy(Most)ThinkersInList() were unreliable when
  destroyed thinkers destroyed more thinkers in the same list.
  Specifically, if the thinker it destroyed caused the very next thinker
  in the list to also be destroyed, it would get lost in the thinker list
  and end up with a NULL node. So just keep iterating through the first
  thinker in the list until there are none left. Since destroying a
  thinker causes it to remove itself from its list, the first thinker will
  always be changing as long as there's something to destroy.