diff3 with the -e (ed script flag) can generate line deletions, add
support for deletions and add a test case to exercise this behaviour.
This functionality was unearthed through comparison of bsd diff3 and gnu
diff3 output.
Reviewed by: pstef
Sponsored by: Klara, Inc.
Differential Revision: https://reviews.freebsd.org/D34912
import bsd diff3 from OpenBSD.
Differences with OpenBSD:
- lots of warning fixed
- no shell wrapper with diff3 actually living in libexec
- capsicumized
Keep it disconnected as it is not yet good enough to replace GNU diff
The motivation to import it now it to allow other people to jump in and also to
have an open development on it
Obtained from: OpenBSD
