Log Message:
Import sdif-1.0nb20140131 as wip/sdif-git.

Sdif is inspired by System V sdiff(1) command. The basic
feature of sdif is making a side-by-side listing of two
different files. All contents of two files are listed on left
and right sides. Center column is used to indicate how
different those lines. No mark means no difference. Added,
deleted and modified lines are marked with `<' and `>'
character.