autoconf-2.50 problems with dnl

[Bruno Haible]

Hi,

I'm running into autoconf errors when using dnl comments.

To reproduce:
  - take gettext-0.10.38,
  - replace m4/libtool.m4 and ltmain.sh with the ones from libtool-1.4,
  - apply the appended patch to m4/gettext.m4,
  - run "./aclocal.sh aclocal -I m4"
  - run "automake --gnits --include-deps Makefile"
  - run "autoconf"

I get
  configure.in:1: error: possibly undefined macro: dnl

This is a regression versus autoconf-2.13.

Note that I really want dnl comments, because if I use "#" the comments
get replicated in the configure script, which I don't want (in order not
to make the configure script larger than it already is).

*** gettext-0.10.38/m4/gettext.m4.bak   Thu May 17 15:35:37 2001
--- gettext-0.10.38/m4/gettext.m4       Thu Jun 14 15:23:09 2001
***************
*** 181,186 ****
--- 181,189 ----
            ac_dir=`echo "$ac_file"|sed 's%/[^/][^/]*$%%'`
            ac_dir_suffix="/`echo "$ac_dir"|sed 's%^\./%%'`"
            ac_dots=`echo "$ac_dir_suffix"|sed 's%/[^/]*%../%g'`
+           dnl In autoconf-2.13 it is called $ac_given_srcdir.
+           dnl In autoconf-2.50 it is called $srcdir.
+           test -n "$ac_given_srcdir" || ac_given_srcdir="$srcdir"
            case "$ac_given_srcdir" in
              .)  top_srcdir=`echo $ac_dots|sed 's%/$%%'` ;;
              /*) top_srcdir="$ac_given_srcdir" ;;