When a header file that includes MLlib.h is included in multiple files, the
linker throws a few multiple definition errors at you. This is fixed by
making a couple of variables extern in the header files:

in globals.h:
  bool _asnd_enabled;
  bool bPowerOff;
  bool bReset;

in MLlib_video.h:
  GXRModeObj *screenMode;
  int _screenWidth, _screenHeight;

in MLlib_input.h:
  WPads Wiimote[WPAD_MAX_WIIMOTES];
  Nunchuks Nunchuk[WPAD_MAX_WIIMOTES];
  CPads CPad[WPAD_MAX_WIIMOTES];
  GH Guitar[WPAD_MAX_WIIMOTES];
  GC_Pads Pad[4];