Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Don't read the newline character to line buffer because lines are passed
to wcscoll(3). Newline characters could cause incorrect results when
comparing lines.

Also, if an input line didn't contain a newline character, it was
omitted from the output. According to my interpretation, SUSv3 requires
that the newline is always printed.

Add regression tests for the cases. [1]

PR: bin/140976
Submitted by: D'Arcy Cain (original version) [1]
Approved by: trasz (mentor)