FinalBurn Alpha Combo

  * Added 4 player support for following games:

    - Marvel Super Heroes Vs. Street Fighter (all clones)
    - Marvel Vs. Capcom (all clones)
    - X-men Vs. Street Fighter (all clones)

 Notes:

  * You *could* join the 4 player versions of above games using
    the official build, but the game will desync immediately.
    All other games will play fine with the official build.

  * Normal mode recordings must be played on normal mode and
    4 player mode recordings must be played on 4 player mode.
    Failing to do so will cause desync while replaying the
    movie.  However, if you load the replay file before any
    game is loaded, it will load the correct mode.

--- How the 4 player mode works ---

  If there are 4 players playing the game, P1 and P2 control left side
  characters, and P3 and P4 control right side characters.  Basically,
  it's (P1 and P2 vs. P3 and P4). On the selection screen, only P1 is
  allowed to select the first character, and then P2 selects the 2nd
  character.  Same goes for the right side players (P3 and then P4).
  The match will start off as P1 vs. P3 until they decide to switch
  with their teammate.  Players cannot control the character while it's
  not their turn, so they must wait for their turn.


--- Rules for 4 player support ---

  * 4 player support for above games are available for both
    off-line and on-line mode.

  * Rules for off-line mode:

    - Requires two players to play against CPU.
    - Requires four players to play against each other.

  * Rules for on-line mode:

    - 1 player at start --->      p1 vs. CPU
    - 2 players at start --> p1 & p2 vs. CPU
    - 3 players at start --> p1 & p2 vs. p3
    - 4 players at start --> p1 & p2 vs. p3 & p4

  * Rules for on-line mode when someone gets dropped/disconnected:

    - p1 dropped ----------> no longer a netplay, Duh!

    - -------------+----------------------+--------------------
      Started with | Dropped/Disconnected | Rule
      -------------+----------------------+--------------------
      2 players    | p2                   |      p1 vs. CPU
      3 players    | p2                   |      p1 vs. p3
      3 players    | p3                   | p1 & p2 vs. CPU
      3 players    | p2 & p3              |      p1 vs. CPU
      4 players    | p2                   |      p1 vs. p3 & p4
      4 players    | p3                   | p1 & p2 vs. p4
      4 players    | p4                   | p1 & p2 vs. p3
      4 players    | p2 & p3              |      p1 vs. p4
      4 players    | p2 & p4              |      p1 vs. p3
      4 players    | p3 & p4              | p1 & p2 vs. CPU
      4 players    | p2 & p3 & p4         |      p1 vs. CPU
      -------------+----------------------+--------------------

--- Bugs regarding to the 4 player mode ---

  * In Marvel Vs. Capcom 4 player mode, player 2 has the control
    in the beginning, not player 1.  Therefore, player 2 has to
    input coins and press start.  After the character selection
    screen appears, things will be normal.  However, if you wait
    until the intro ends (after attract mode is started), player 1
    has the control first (which is the way it should be).  The RAM
    monitoring for supporting 4 player mode is based on MAME32k.
    I wasn't able to test this on mame32k, so I don't know if same
    thing happens on MAME32k or not.

  * When you generate Romcenter/ClrMamePro dat files, you will
    notice that the 4 player version of above games are listed as
    seperate set of roms. Due to the Game driver structure, it was
    either making them listed as seperate roms, or making them use
    same file names for the game cfg file.  Since switching between
    the normal and 4 player mode could screw up input setting, I
    made it to use different file names, and therefore, listed as
    new set of roms in the dat file. The 4 player versions, however,
    use same roms as normal versions since these are not a rom hacks,
    but input hacks.  Therefore, their status will be same as your
    normal romset status.

--- Credits ---

  * FBA Team (http://fba.emuunlim.com)

  * The F***ing Rabbit (http://emulators.at/uomame32k)
    - RAM monitoring code for 4 player support is based on MAME32k.
