[r1884] Various command-line parameter bugs

[printz]

• -loadgame <n>
  
  If I tell Eternity to load an inexistent file (empty slot), it will start with a blank screen and no music (the console is being pulled down to show me the error message, but the screen is blank). The game menu will work and I'll be able to start a new game. The screen will refresh normally when I start a new game.
  
  If I tell Eternity to load at startup from a game with an invalid WAD, it quits with a memory error, instead of showing a dedicated error message. It also happens when trying to load a wrong wad savegame at runtime.
  

  Z_Malloc: Failure trying to allocate 1647259136 bytes
  Source: .\source\p_saveg.cpp:1499
  

• -recordfrom <n> <demoname>
  
  If I give this one a wrong WAD savegame, it will crash. Here's the log: http://pastebin.com/aCe6jr8G
  
  It also crashes if I give in an empty save slot. Log here: http://pastebin.com/a61i0rq1
  
  
• -play <demoname>
  
  If I say -play instead of -playdemo, the demo file gets loaded, but not played back.
  
  
• -avg
  
  Instead of 20 minutes, it seems to set the timer to 700 hours, because it is still written in tics in the program. Also, the parameter fails if it's the last. I also reported about this in the chatroom, Ladna saw it. Note that I didn't have the patience to test -avg in 20 minutes.
  
  
• -vanilla
  (not a bug)
  
  It seems that unlike other gameplay-altering parms (-nomonsters, -respawn, -fast and probably others), -vanilla works like in vanilla Doom: only with autostart or netgame, and gets reset at the next new game. Though I can guess why: it would be harder to reset by the user.
  

[Quasar]

GIGO principle - "Garbage in, garbage out" - applies to several of these.

Doom had no tolerance built in for any deviation from its expected binary file and data lump formats. We have been slowly increasing this tolerance by adding code that works around corrupt files, accounts for zero-length or nonsensical inputs, etc. However for various reasons such as development time and difficulty, many code segments will still crash just as hard as they would have in vanilla if you challenge them. In short, don't challenge them :P Since you have pointed out these issues, I will probably take time to address some of them, though.

[Csonicgo]

I use Austin Virtual Gaming mode at cons, so if EE could support it, that'd be boss.