Extract diff display logic from Diff::LCS::Ldiff

[mvz]

I'm looking for a way to quickly display a diff of two strings. The logic in Diff::LCS::Ldiff seems to do the right thing, but it comes with extra stuff needed for a command line program. It would be nice if this were split so the hunk merging and output logic can be re-used.

[halostatue]

Patches for this will be considered; I have no time to implement this.