Sync with FreeBSD:

Sync with FreeBSD:

* Change semantics of -i (in-place editing) so that it treats each file
  independently from other files (desired in most practical cases). Keep
  the previous semantics (use a single continuous address space covering
  all files to edit in-place) under -I.

* Add -l option (make output line buffered).

* Make the 'y' command (translate) aware of multibyte characters.

* Add case-insensitive matching, using the 'I' flag, a la GNU sed.

* Remove 3rd clause.

* Raise WARNS to 6.

* Miscellaneous fixes and style(9) issues.