Over-zealous error message

[Tim Van Holder]

I'm not sure if this has been reported before (it probably has),
but when bootstrapping libtool 1.4.cvs (and the same happens
with the 1.4 release) using autoconf 2.50 (or CVS HEAD), I get
these errors:

configure.in:19: error: possibly undefined macro: AC_LIBLTDL_INSTALLABLE
configure.in:19: error: possibly undefined macro: AC_LIBLTDL_CONVENIENCE

The offending lines are:

    AC_MSG_WARN([*** The top-level configure must select either])
    AC_MSG_WARN([*** [AC_LIBLTDL_INSTALLABLE] or [AC_LIBLTDL_CONVENIENCE].])
    AC_MSG_ERROR([*** Maybe you want to --enable-ltdl-install?])

As you can see, they're properly quoted.
Adding extra quoting still results in the above errors (and adds the excess
quotes to the output messages.

Even the usual away to avoid such misidentification:

    AC_MSG_WARN([*** The top-level configure must select either])
    AC_MSG_WARN([*** [A]C_LIBLTDL_INSTALLABLE or [A]C_LIBLTDL_CONVENIENCE.])
    AC_MSG_ERROR([*** Maybe you want to --enable-ltdl-install?])

does not help; the errors simply get reported in configure instead of
configure.in:

configure:1191: error: possibly undefined macro: AC_LIBLTDL_INSTALLABLE
configure:1191: error: possibly undefined macro: AC_LIBLTDL_CONVENIENCE