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

#!/bin/sh
# a test for issue586

hg init a
cd a
echo a > a
hg ci -Ama

hg init ../b
cd ../b
echo b > b
hg ci -Amb

hg pull -f ../a
hg merge
hg rm -f a
hg ci -Amc

hg st -A