bdiff: tweaks for large files - adjust the common line threshold to .1% this speeds up a delta of 7M lines of source from 10m to 40s - adjust the scaling of the hash array down a bit as it was raising the peak memory usage significantly

digraph G {
	-1 -> 0
	0 -> 1
	0 -> 2
	2 -> 3
	1 -> 3
}