pdksh: document that KSH_VERSION is not reliable

[Ralf Wildenhues]

We've had this issue a bit ago; I only now stumbled over the fact that
the documentation needed an update, too.

OK to apply?

Cheers,
Ralf

        * doc/autoconf.texi (Shellology) <pdksh>: Document that pdksh as
        native /bin/sh may not set KSH_VERSION (seen on OpenBSD).

Index: doc/autoconf.texi
===================================================================
RCS file: /cvsroot/autoconf/autoconf/doc/autoconf.texi,v
retrieving revision 1.949
diff -u -r1.949 autoconf.texi
--- doc/autoconf.texi   15 Feb 2006 07:00:29 -0000      1.949
+++ doc/autoconf.texi   19 Feb 2006 18:42:59 -0000
@@ -9916,12 +9965,12 @@
 @prindex @samp{pdksh}
 A public-domain clone of the Korn shell called @command{pdksh} is widely
 available: it has most of the @samp{ksh88} features along with a few of
-its own.  Similarly to Bash, you can detect whether you are
-running @command{pdksh} by testing whether @code{KSH_VERSION} is set,
-and you can require Posix compatibility by running @samp{set
--o posix}.  Unfortunately, with @command{pdksh} 5.2.14 (the latest
-stable version as of January 2006) Posix mode is buggy and causes
address@hidden to depart from Posix in at least one respect:
+its own.  It will usually set @code{KSH_VERSION}, except if invoked as
address@hidden/bin/sh} on OpenBSD, and similarly to Bash you can require
+Posix compatibility by running @samp{set -o posix}.  Unfortunately, with
address@hidden 5.2.14 (the latest stable version as of January 2006)
+Posix mode is buggy and causes @command{pdksh} to depart from Posix in
+at least one respect:
 
 @example
 $ echo "`echo \"hello\"`"