allow commands like:
	neponset#  dd -count 1 -if data -iseek 8589934591 -of /dev/null
	1+0 records in
	1+0 records out
prior behavior:
	neponset# dd -count 1 -if data -iseek 8589934591 -of /dev/null
	dd: argument 8589934591 out of range