Fixed the ghost auto-fired buttons with original NES controllers.
Found and fixed another bug: the missing pull-up on the DATA which caused the a similar ghosting when no controller was present.

As an extra feature I have unified the button mapping. Now A,B,Sel,Start on NES activates the same PC buttons as the SNES controllers (1,2,7,8 respectively).

//
// USB Joystick Mapping
//  
//   USB       == SNES ==     == NES ==
//  Y Axis   -  Up/Down    -   Up/Down  
//  X Axis   - Left/Right  -  Left/Right
//  Button 1 -     A       -      A     
//  Button 2 -     B       -      B     
//  Button 3 -     x       -      -     
//  Button 4 -     Y       -      -     
//  Button 5 -   Top L     -      -   
//  Button 6     Top R     -      -   
//  Button 7 -   Select    -    Select  
//  Button 8 -   Start     -    Start