util/rundiff:
Make sure Algorithm::Diff is loaded only if you need it
(so it's ok if you don't have it installed).
Add command-line options for things you might want to change:
- diff algorithm
- # of context lines
- # of lines of lookahead
--HG--
extra : convert_revision : b3ba02e1816eee286f47eb28ab578fa4734bac3a
7651e19cd1