patch taken from openbsd.
Ingo Schwarze says:
If you call the col(1) utility with the -f option, permitting forward
half-line feeds in the output stream, and the input stream actually
contains half-line feeds in either direction, you end up with corrupt
output, containing meaningless escape-digitnine sequences instead of
the required escape-tab sequences.
$ hexdump -C half.txt
00000000 61 1b 09 62 1b 09 63 0a |a..b..c.|
00000008
$ col -f < half.txt | hexdump -C
00000000 61 1b 39 0d 20 62 1b 39 0d 20 20 63 0a |a.9. b.9. c.|
0000000d
Note how the third character changes from 0x09 to 0x39.
OK to commit the following fix? Don't worry, it isn't dangerous,
it only changes two *bits*, only a quarter of a byte.
The bug was introduced by the original author, Michael Rendell,
and committed by Keith Bostic on May 22, 1990 (SCCS rev. 5.1).
The following operating systems are affected:
* 4.3BSD Reno, BSD Net/2, 4.4BSD, 4.4BSD Lite1, 4.4BSD Lite2
* All versions of 386BSD, NetBSD, OpenBSD, FreeBSD and DragonFly
* All versions of Debian GNU/Linux and probably many other Linuxes
