Log Message:
update to 1.3, prepare for forthcoming stella-sdl, take maintanership

Changes since 1.1:
* Improved TIA sound system so that games with digitized audio work
* Added saving and loading of game state to the core; X11, SDL,
  and DOS versions current support saving and loading game state
* Added support for F4 bankswitching method
* Pitfall II DPC sound emulation completed
* Support added for the Commavid (CV) bankswitching method.
* Support added for the Megaboy cartridge.
* Improved Supercharger emulation including a new BIOS that shows
  the vertical blue progress bars like the real thing.
* Added snapshot support to the X11 and SDL versions. Pressing F12
  saves the current screen in PNG format. Requires PNG library.
* Added pause functionality to the core. Implemented in DOS, X11,
  and SDL versions for now.