fix crash due to offsets being truncated to 32 bits.
opted to track offsets as 64 bits to allow for 64-bit address spaces
in userland.

recipe:
	ramfs -m /n/junk
	cp /bin/8c /n/junk
	>/dev/null dd -if /n/junk/8c -iseek 81191 -count 1 -bs 81191