IFS unset in buggy ash version

[Ralf Wildenhues]

The ash-0.3.8-20 package of Fedora Core 3 unsets $IFS upon startup.
This exposed a flaw in Libtool[1] (and it is a bug in ash as their
documentation claims otherwise).

Autoconf might thus want to consider putting its

| # IFS
| # We need space, tab and new line, in precisely that order.
| as_nl='
| '
| IFS="   $as_nl"

not only in AS_PREPARE, but also in AS_SHELL_SANITIZE.

Regards,
Ralf

[1] http://lists.gnu.org/archive/html/libtool-patches/2005-03/msg00152.html
and thread.