image.c: Added support for loading a default battery, instead of a fixed fill value, when no
battery is found. This allows for loading factory formatted sram/nvram from softlist. [Fabio Priuli]

(MESS) nes.c: Fixed Silva Saga, which relies on SRAM not being 0x00 filled from factory,
with many thanks to naruko for investigating the problem. [Fabio Priuli]