Revision 4290

This patch implements a "flash friendly" value for initialized areas of flash. 
It makes the write part of flashrom dramatically faster with small
payloads like filo; and it also eliminates unnecessary wear on flash
by not writing zeros (it's unlikely this really matters; let me know 
next time you flash a BIOS flash 100,000 times!). 

More importantly, it allows for future partial flash upgrades with cbfs. 

Note that uninitialized_flash_value is a global that can, if we ever need it, 
be set by an argument in main. Assuming we ever see a flash where the 
"erased" value is 0, not 0xff. 

At the same time, "erased" value has been "1" on every EEPROM or 
FLASH I've used for some time now. 

Signed-off-by: Ronald G. Minnich <rminnich@gmail.com>
Acked-by: Peter Stuge <peter@stuge.se>